Comfort Systems USA (FIX) had the highest return in May 2001 by a large-cap US stock, returning 100%.

ASSET	MONTH	% RETURN
Comfort Systems USA (FIX)	May 2001	100.01%
Tyler Technologies (TYL)	May 2001	70%
F5 Networks (FFIV)	May 2001	55.76%
Service Corporation International (SCI)	May 2001	53.48%
Insmed (INSM)	May 2001	48.77%
EXACT Sciences (EXAS)	May 2001	46.19%
Hecla Mining (HL)	May 2001	45.83%
Neurocrine Biosciences (NBIX)	May 2001	45.6%
Take-Two Interactive Software (TTWO)	May 2001	45.38%
Kinross Gold (KGC)	May 2001	39.29%
Illumina (ILMN)	May 2001	35.71%
Entegris (ENTG)	May 2001	34.66%
Dr Reddy’s Laboratories Ltd ADR (RDY)	May 2001	33.42%
Telkom Indonesia (Persero) Tbk PT ADR Rep 100 B (TLK)	May 2001	31.94%
Quanta Services (PWR)	May 2001	31.88%
Incyte (INCY)	May 2001	31.8%
Expeditors International of Washington (EXPD)	May 2001	29.01%
Charles River Laboratories (CRL)	May 2001	27.82%
EMCOR (EME)	May 2001	25.18%
Teledyne Technologies (TDY)	May 2001	25%
PG&E (PCG)	May 2001	24.59%
Global Payments (GPN)	May 2001	24.56%
CACI International (CACI)	May 2001	23.26%
Biogen (BIIB)	May 2001	23.2%
Hasbro (HAS)	May 2001	22.95%

Large-cap stocks are treated as having a market cap of $10B+.