WESTFIELD CAPITAL MANAGEMENT CO LP

CIK

1177719

Location

BOSTON, MA

Portfolio Value

Large $23,754,373,780

Diversification

Diversified

Filing Date

Global Rank

#247 / 8,621 ▲ 3 · as of Mar 2026

Top Industry

Biotechnology 10.4%

3Y Alpha vs SPY

-2.3%

Period ended 4 months ago

Filed May 11, 2026 · 3mo

25 quarters · since Mar 2020

Clone Performance

Jul 2023–Jul 2026 · vs SPY

Hypothetical growth of buying every stock this filer reported holding, rebalancing on each filing and indexed to the same start. Option positions cannot be bought this way and are left out.

Cloned portfolio

+61.1%

SPY

+67.9%

Annualised alpha

-1.6%

Max drawdown

−25.7%

Estimate. 13F holdings are quarter-lagged, so the clone rebalances about 45 days after each period end — when the filing becomes public — and it excludes option and short positions. It tracks 100% of reported value on average across 13 quarters. Past performance does not predict future results.

Portfolio Concentration

243 positions · as of Mar 31, 2026 · Δ vs Dec 31, 2025

Top Position

4.6%

−0.0 pts

Top 5

19.2%

−0.1 pts

Top 10

30.4%

+0.5 pts

HHI

143

Diversified+2

Portfolio Trend

25 quarters · across all stocks

Sector Breakdown

As of Mar 31, 2026

Sector	% Portfolio	Value	Positions
Technology	28.5%	$6,775,203,452	58
Industrials	25.3%	$6,018,658,027	43
Healthcare	15.6%	$3,709,874,328	49
Consumer Cyclical	10.5%	$2,501,827,195	27
Financial Services	8.9%	$2,111,651,462	32
Communication Services	5.9%	$1,399,076,589	8
Energy	2.7%	$642,147,704	10
Consumer Defensive	0.9%	$217,580,314	6
Basic Materials	0.6%	$144,528,023	4
Utilities	0.5%	$127,757,381	4
Real Estate	0.4%	$106,069,305	2

Last Quarter's Activity

Export CSV

Mar 31, 2026 vs Dec 31, 2025

Added To

Positions the filer increased

25 positions

Ticker	Company	Δ Shares	Shares	Value
CELH	Celsius Holdings, Inc.	+2,224,696	3,768,911	$133,720,962
BRZE	Braze, Inc.	+1,786,631	3,973,906	$93,823,920
PR	Permian Resources Corp	+1,530,271	7,481,457	$159,504,663
ADPT	Adaptive Biotechnologies Corp	+1,376,237	5,436,718	$18,865,411
APG	APi Group Corp	+1,181,574	4,634,929	$187,807,323
KEY	Keycorp /New/	+1,153,037	5,193,334	$104,126,346
IOT	Samsara Inc.	+1,118,851	5,072,821	$160,757,697
INSM	INSMED Inc	+1,035,938	1,468,459	$240,122,415
RGTI	Rigetti Computing, Inc.	+959,535	1,895,313	$26,610,194
DT	Dynatrace, Inc.	+852,886	4,209,594	$155,670,786
GH	Guardant Health, Inc.	+823,349	1,362,539	$125,857,727
ALAB	Astera Labs, Inc.	+664,819	860,113	$94,268,384
RYTM	Rhythm Pharmaceuticals, Inc.	+661,965	1,929,123	$167,775,827
RKLB	Rocket Lab Corp	+580,168	3,172,611	$203,745,078
BROS	Dutch Bros Inc.	+533,741	2,313,357	$117,194,665
TOST	Toast, Inc.	+522,536	1,790,873	$47,476,043
PLTR	Palantir Technologies Inc.	+519,972	674,557	$98,674,197
FTAI	FTAI Aviation Ltd.	+497,602	2,848,227	$697,815,615
CRDO	Credo Technology Group Holding Ltd	+455,532	926,219	$86,944,177
ARES	Ares Management Corp	+421,587	1,572,787	$171,591,061
CALX	Calix, Inc	+400,809	1,546,101	$75,743,487
STEP	StepStone Group Inc.	+391,470	1,177,971	$56,212,776
BIRK	Birkenstock Holding plc	+383,978	2,338,779	$83,798,451
PLXS	Plexus Corp	+379,293	384,493	$77,875,212
NFLX	Netflix Inc	+372,447	1,969,994	$189,414,923
No positions match the current search.

Trimmed

Positions the filer reduced

25 positions

Ticker	Company	Δ Shares	Shares	Value
GENI	Genius Sports Ltd	−5,744,053	207,150	$917,674
BAC	Bank Of America Corp /De/	−2,756,724	1,066,885	$52,010,643
OPCH	Option Care Health, Inc.	−1,582,491	1,182,814	$31,841,352
DXCM	Dexcom Inc	−1,412,615	27,074	$1,700,247
FITB	Fifth Third Bancorp	−1,361,504	2,385,422	$110,826,706
RVMD	Revolution Medicines, Inc.	−1,288,435	1,556,578	$151,377,210
HQY	Healthequity, Inc.	−1,239,604	712,848	$59,572,707
MASI	Masimo Corp	−1,180,820	341,229	$60,694,402
SMTC	Semtech Corp	−1,168,018	1,280,594	$98,464,872
CWST	Casella Waste Systems Inc	−842,734	822,492	$65,256,515
APLD	Applied Digital Corp.	−492,305	542,092	$12,869,264
ABBV	AbbVie Inc.	−409,165	10,619	$2,309,526
LEGN	Legend Biotech Corp	−401,202	5,763,475	$104,261,262
DSGX	Descartes Systems Group Inc	−391,967	801,902	$57,384,107
PODD	Insulet Corp	−384,786	1,682	$352,950
ASND	Ascendis Pharma A/S	−372,256	4,813,440	$1,100,978,131
VRT	Vertiv Holdings Co	−356,020	1,921,696	$481,538,583
RMBS	Rambus Inc	−347,656	14,436	$1,241,929
WCN	Waste Connections, Inc.	−308,810	4,466	$725,457
MRVL	Marvell Technology, Inc.	−274,426	1,673,381	$165,748,388
COHR	Coherent Corp.	−268,479	396,644	$94,484,567
AMD	Advanced Micro Devices Inc	−245,435	5,020	$1,021,218
UNH	Unitedhealth Group Inc	−227,511	2,767	$748,722
RRX	Regal Rexnord Corp	−211,383	681,717	$127,658,325
DHR	Danaher Corp /De/	−210,995	110,492	$20,949,283
No positions match the current search.

New Positions

Positions the filer opened this quarter

25 positions

Ticker	Company	Shares	Value
LNG	Cheniere Energy, Inc.	459,044	$130,258,325
AS	Amer Sports, Inc.	3,937,521	$129,623,191
AIG	American International Group, Inc.	1,458,711	$109,768,002
JLL	Jones Lang Lasalle Inc	347,779	$105,836,105
ROST	Ross Stores, Inc.	471,916	$102,231,163
WWD	Woodward, Inc.	272,185	$97,420,455
ANET	Arista Networks, Inc.	780,402	$95,817,757
LTH	Life Time Group Holdings, Inc.	3,185,515	$85,817,774
MS	Morgan Stanley	496,558	$81,718,550
MTZ	Mastec Inc	249,980	$80,428,565
GWRE	Guidewire Software, Inc.	486,581	$72,773,054
LOW	Lowes Companies Inc	300,962	$71,111,301
NAMS	NewAmsterdam Pharma Co N.V.	2,202,913	$70,515,245
MCHP	Microchip Technology Inc	970,295	$62,690,759
IBP	Installed Building Products, Inc.	208,248	$55,216,957
GKOS	GLAUKOS Corp	482,219	$51,915,697
CDE	Coeur Mining, Inc.	2,738,846	$51,408,139
MAR	Marriott International Inc /Md/	153,219	$50,113,338
MDGL	Madrigal Pharmaceuticals, Inc.	94,813	$49,631,761
NXPI	NXP Semiconductors N.V.	247,996	$48,820,492
PL	Planet Labs PBC	1,637,041	$45,755,295
ENTG	Entegris Inc	371,686	$43,576,466
RIOT	Riot Platforms, Inc.	3,499,880	$43,258,516
CPAY	Corpay, Inc.	143,120	$41,646,488
MU	Micron Technology Inc	100,434	$33,930,622
No positions match the current search.

Sold Out

Positions the filer fully exited

25 positions

Ticker	Company	Shares	Value
CVLT	Commvault Systems Inc	1,057,077	$132,515,172
TEAM	Atlassian Corp	812,215	$131,692,540
ADMA	Adma Biologics, Inc.	6,992,907	$127,550,623
ALKT	Alkami Technology, Inc.	4,118,355	$95,010,449
ORCL	Oracle Corp	474,397	$92,464,719
BURL	Burlington Stores, Inc.	302,307	$87,321,376
DKNG	DraftKings Inc.	2,383,054	$82,120,040
TRU	TransUnion	933,553	$80,052,169
VMC	Vulcan Materials CO	254,044	$72,458,429
SLAB	Silicon Laboratories Inc.	547,403	$71,545,572
AJG	Arthur J. Gallagher & Co.	259,491	$67,153,675
OWL	Blue Owl Capital Inc.	4,423,608	$66,088,703
PRI	Primerica, Inc.	234,597	$60,610,480
IRTC	iRhythm Holdings, Inc.	325,063	$57,679,178
BIO	Bio-Rad Laboratories, Inc.	165,107	$50,025,769
FNB	Fnb Corp/Pa/	2,903,113	$49,643,232
BLDR	Builders FirstSource, Inc.	475,697	$48,944,464
RYAN	Ryan Specialty Holdings, Inc.	814,334	$42,044,064
NIQ	NIQ Global Intelligence plc	2,388,660	$39,389,003
RBLX	Roblox Corp	461,670	$37,409,120
FORM	Formfactor Inc	449,604	$25,078,911
BCYC	Bicycle Therapeutics PLC	3,016,026	$21,353,464
CTAS	Cintas Corp	42,271	$7,949,906
CME	Cme Group Inc.	21,785	$5,949,047
SLB	Slb Limited/Nv	120,910	$4,640,525
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

243 positions · $23,754,373,780 total · as of Mar 31, 2026

All sectors Basic Materials Communication Services Consumer Cyclical Consumer Defensive Energy Financial Services Healthcare Industrials Real Estate Technology Utilities

Showing 1–50 of 243 positions by value · page 1 of 5

Ticker	Company	Type	Shares	Δ Shares	Value (USD)	% Δ Value	% of Portfolio
NVDA	Nvidia Corp Technology	Added	6,317,039	+365,990	$1,101,691,601	−0.7%	4.64%
ASND	Ascendis Pharma A/S Healthcare	Reduced	4,813,440	-372,256	$1,100,978,131	−0.4%	4.63%
FIX	Comfort Systems USA Inc Industrials	Reduced	620,915	-47,920	$856,235,575	+37.2%	3.60%
AAPL	Apple Inc. Technology	Reduced	3,133,113	-141,205	$795,152,748	−10.7%	3.35%
FTAI	FTAI Aviation Ltd. Industrials	Added	2,848,227	+497,602	$697,815,615	+50.8%	2.94%
MSFT	Microsoft Corp Technology	Added	1,649,513	+28,294	$610,600,227	−22.1%	2.57%
GOOGL	Alphabet Inc. Communication Services	Reduced	2,026,744	-151,734	$582,810,504	−14.5%	2.45%
HWM	Howmet Aerospace Inc. Industrials	Added	2,289,697	+70,572	$527,683,570	+16.0%	2.22%
VRT	Vertiv Holdings Co Industrials	Reduced	1,921,696	-356,020	$481,538,583	+30.5%	2.03%
AMZN	Amazon Com Inc Consumer Cyclical	Reduced	2,279,654	-51,116	$474,783,538	−11.7%	2.00%
AXON	Axon Enterprise, Inc. Industrials	Added	1,064,134	+232,957	$451,927,068	−4.3%	1.90%
AVGO	Broadcom Inc. Technology	Added	1,236,925	+124,607	$382,840,656	−0.6%	1.61%
LLY	ELI LILLY & Co Healthcare	Added	364,579	+87,030	$335,328,826	+12.4%	1.41%
TPR	Tapestry, Inc. Consumer Cyclical	Added	2,198,862	+100,758	$310,281,416	+15.7%	1.31%
META	Meta Platforms, Inc. Communication Services	Reduced	526,822	-128,461	$301,410,670	−30.3%	1.27%
LPLA	LPL Financial Holdings Inc. Financial Services	Added	881,506	+255,944	$265,183,449	+18.7%	1.12%
MKSI	Mks Inc Technology	Added	1,046,763	+206,990	$240,556,605	+79.3%	1.01%
INSM	INSMED Inc Healthcare	Added	1,468,459	+1,035,938	$240,122,415	+219.0%	1.01%
PCVX	Vaxcyte, Inc. Healthcare	Added	3,646,138	+106,421	$211,877,079	+29.7%	0.89%
RKLB	Rocket Lab Corp Industrials	Added	3,172,611	+580,168	$203,745,078	+12.7%	0.86%
NFLX	Netflix Inc Communication Services	Added	1,969,994	+372,447	$189,414,923	+26.5%	0.80%
APG	APi Group Corp Industrials	Added	4,634,929	+1,181,574	$187,807,323	+42.1%	0.79%
PWR	Quanta Services, Inc. Industrials	Added	331,816	+58,288	$182,173,620	+57.8%	0.77%
GEV	GE Vernova Inc. Industrials	Added	199,306	+21,372	$173,974,207	+49.6%	0.73%
ARES	Ares Management Corp Financial Services	Added	1,572,787	+421,587	$171,591,061	−7.8%	0.72%
RYTM	Rhythm Pharmaceuticals, Inc. Healthcare	Added	1,929,123	+661,965	$167,775,827	+23.7%	0.71%
TSM	Taiwan Semiconductor Manufacturing Co Ltd Technology	Added	493,504	+47,309	$166,779,676	+23.0%	0.70%
MRVL	Marvell Technology, Inc. Technology	Reduced	1,673,381	-274,426	$165,748,388	+0.1%	0.70%
BE	Bloom Energy Corp Industrials	Added	1,191,572	+46,276	$161,446,090	+62.2%	0.68%
IOT	Samsara Inc. Technology	Added	5,072,821	+1,118,851	$160,757,697	+14.7%	0.68%
AME	Ametek Inc/ Industrials	Reduced	745,832	-154,384	$159,876,547	−13.5%	0.67%
PR	Permian Resources Corp Energy	Added	7,481,457	+1,530,271	$159,504,663	+91.0%	0.67%
DT	Dynatrace, Inc. Technology	Added	4,209,594	+852,886	$155,670,786	+7.0%	0.66%
RVMD	Revolution Medicines, Inc. Healthcare	Reduced	1,556,578	-1,288,435	$151,377,210	−33.2%	0.64%
NTRA	Natera, Inc. Healthcare	Added	754,729	+40,037	$150,938,252	−7.8%	0.64%
FN	Fabrinet Technology	Added	284,874	+94,704	$148,567,488	+71.6%	0.63%
ABVX	Abivax S.A. Healthcare	Added	1,322,938	+312,972	$147,309,146	+8.2%	0.62%
NOW	ServiceNow, Inc. Technology	Reduced	1,394,187	-82,616	$145,762,250	−35.6%	0.61%
FTI	TechnipFMC plc Energy	Added	2,033,755	+81,328	$140,593,483	+61.6%	0.59%
RCL	Royal Caribbean Cruises Ltd Consumer Cyclical	Added	505,765	+57,112	$139,176,412	+11.2%	0.59%
HLT	Hilton Worldwide Holdings Inc. Consumer Cyclical	Added	457,425	+99,704	$139,093,794	+35.4%	0.59%
V	Visa Inc. Financial Services	Reduced	456,548	-147,378	$137,987,067	−34.9%	0.58%
COR	Cencora, Inc. Healthcare	Added	436,909	+117,694	$137,250,593	+27.3%	0.58%
ITT	Itt Inc. Industrials	Added	703,309	+115,863	$134,001,463	+31.5%	0.56%
CELH	Celsius Holdings, Inc. Consumer Defensive	Added	3,768,911	+2,224,696	$133,720,962	+89.3%	0.56%
NXT	Nextpower Inc. Technology	Added	1,107,346	+17,046	$133,490,560	+40.6%	0.56%
LNG	Cheniere Energy, Inc. Energy	NEW	459,044	NEW	$130,258,325	NEW	0.55%
AS	Amer Sports, Inc. Consumer Cyclical	NEW	3,937,521	NEW	$129,623,191	NEW	0.55%
RRX	Regal Rexnord Corp Industrials	Reduced	681,717	-211,383	$127,658,325	+1.9%	0.54%
MSCI	MSCI Inc. Financial Services	Added	233,764	+25,972	$126,001,133	+5.7%	0.53%