Regeneron Pharmaceuticals (REGN) had the highest return in March 2011 by a US stock in the S&P 500 (GSPC), returning 23.4%.

ASSET	MONTH	% RETURN
Regeneron Pharmaceuticals (REGN)	March 2011	23.36%
Western Digital (WDC)	March 2011	21.7%
Westinghouse Air Brake Technologies (WAB)	March 2011	19.15%
Builders FirstSource (BLDR)	March 2011	17.84%
Ulta Beauty (ULTA)	March 2011	16.26%
Insulet (PODD)	March 2011	16.23%
Huntington Ingalls Industries (HII)	March 2011	16.18%
Motorola Solutions (MSI)	March 2011	15.54%
Tesla (TSLA)	March 2011	15.39%
Incyte (INCY)	March 2011	15.36%
Netflix (NFLX)	March 2011	15.32%
Tractor Supply (TSCO)	March 2011	14.87%
Lululemon Athletica (LULU)	March 2011	14.83%
Contura Energy (CTRA)	March 2011	14.7%
Seagate Technology (STX)	March 2011	14.14%
Old Dominion Freight Line (ODFL)	March 2011	13.74%
Expedia (EXPE)	March 2011	13.53%
Molina Healthcare (MOH)	March 2011	13.48%
Fair Isaac (FICO)	March 2011	12.85%
MarketAxess (MKTX)	March 2011	12.72%
T-Mobile US (TMUS)	March 2011	12.62%
Booking (BKNG)	March 2011	12.54%
Chipotle Mexican Grill (CMG)	March 2011	12.09%
Cooper Companies, Inc Common Stock (COO)	March 2011	12.02%
Domino’s Pizza (DPZ)	March 2011	11.76%