DexCom (DXCM) had the best month in April 2008 by a large-cap US stock in April 2008, returning 87.8%.

ASSET	MONTH	% RETURN
DexCom (DXCM)	April 2008	87.8%
Baidu (BIDU)	April 2008	49.44%
Ford Motor (F)	April 2008	43.15%
Celestica (CLS)	April 2008	38.4%
Mizuho Financial (MFG)	April 2008	37.93%
Visa Inc Class A (V)	April 2008	32.33%
Cummins (CMI)	April 2008	32.28%
Telefonaktiebolaget LM Ericsson B ADR (ERIC)	April 2008	31.03%
Woodward (WWD)	April 2008	29.06%
Westlake Chemical (WLK)	April 2008	29.03%
Sumitomo Mitsui Financial (SMFG)	April 2008	28.88%
Insulet (PODD)	April 2008	28.85%
Bunge (BG)	April 2008	28.61%
Centene (CNC)	April 2008	28.46%
CF Industries (CF)	April 2008	28.36%
Alphabet Inc Class A (GOOGL)	April 2008	28.27%
Monolithic Power Systems (MPWR)	April 2008	27.79%
ON Semiconductor (ON)	April 2008	27.69%
Canadian Natural Resources (CNQ)	April 2008	27.19%
Micron Technology (MU)	April 2008	26.35%
MercadoLibre (MELI)	April 2008	24.83%
Deckers Outdoor (DECK)	April 2008	24.59%
Mitsubishi UFJ Financial Group Inc ADR (MUFG)	April 2008	23.9%
BHP (BHP)	April 2008	23.69%
Orix Corp Ads (IX)	April 2008	23.16%

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