National Grid PLC ADR (NGG) had the highest return between 2005 and 2006 by a large-cap US stock, returning 1,088,619%.

ASSET	YEARS	% RETURN
National Grid PLC ADR (NGG)	2005-2006	1,088,619.05%
Monster Beverage (MNST)	2005-2006	620.59%
Banco Bradesco SA ADR (BBD)	2005-2006	551.89%
Suzano Papel e Celulose SA ADR (SUZ)	2005-2006	444.85%
Tenaris SA ADR (TS)	2005-2006	432.91%
Allegheny Technologies (ATI)	2005-2006	324.78%
Illumina (ILMN)	2005-2006	317.3%
Akamai Technologies (AKAM)	2005-2006	309.24%
Vertex Pharmaceuticals (VRTX)	2005-2006	249.72%
Wheaton Precious Metals (WPM)	2005-2006	238.08%
Hologic (HOLX)	2005-2006	236.03%
Clean Harbors (CLH)	2005-2006	218.49%
NVIDIA (NVDA)	2005-2006	204.09%
Agnico Eagle Mines (AEM)	2005-2006	203.34%
CBRE Group Inc Class A (CBRE)	2005-2006	196.87%
Nasdaq (NDAQ)	2005-2006	193.24%
Companhia de Saneamento Basico do Estado de Sao Paulo SABESP ADR (SBS)	2005-2006	188.62%
Sumitomo Mitsui Financial (SMFG)	2005-2006	188.28%
Woori Financial (WF)	2005-2006	187.4%
Southern Copper (SCCO)	2005-2006	182.69%
Credicorp (BAP)	2005-2006	181.92%
Alnylam Pharmaceuticals (ALNY)	2005-2006	179.01%
Alamos Gold (AGI)	2005-2006	177.67%
Petroleo Brasileiro Petrobras SA ADR (PBR)	2005-2006	176.9%
Petróleo Brasileiro SA - Petrobras (PBR.A)	2005-2006	176.78%

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