Genmab A-S (GMAB) had the highest return in September 2013 by a US stock with a market cap of $20B+, returning 40.5%.

ASSET	MONTH	% RETURN
Genmab A-S (GMAB)	September 2013	40.49%
Centrais Electricas Brasileiras (EBR)	September 2013	27.72%
Regeneron Pharmaceuticals (REGN)	September 2013	27.19%
Micron Technology (MU)	September 2013	26.78%
Trip Group Ltd ADR (TCOM)	September 2013	24.89%
Axon Enterprise (AXON)	September 2013	24.83%
Ciena (CIEN)	September 2013	23.14%
Alnylam Pharmaceuticals (ALNY)	September 2013	21.37%
Cheniere Energy (LNG)	September 2013	20.68%
ICICI Bank (IBN)	September 2013	20.62%
Facebook (META)	September 2013	20.05%
Nokia (NOK)	September 2013	19.43%
Ulta Beauty (ULTA)	September 2013	18.72%
Banco Bradesco SA ADR (BBD)	September 2013	18.23%
Banco Santander Brasil SA ADR (BSBR)	September 2013	18.2%
Petróleo Brasileiro SA - Petrobras (PBR.A)	September 2013	17.98%
Delta Air Lines (DAL)	September 2013	17.66%
Centrais Elétricas Brasileiras SA - Eletrobrás (EBR.B)	September 2013	17.63%
Elbit Systems (ESLT)	September 2013	17.23%
Tyler Technologies (TYL)	September 2013	17.1%
Las Vegas Sands (LVS)	September 2013	17.04%
Banco Bradesco S/A ADR (BBDO)	September 2013	16.66%
Banco Bilbao Viscaya Argentaria SA ADR (BBVA)	September 2013	16.3%
Applied Materials (AMAT)	September 2013	15.33%
Itau Unibanco Banco (ITUB)	September 2013	15.08%