Natera (NTRA) had the highest return in August 2017 by a large-cap US stock, returning 52.1%.

ASSET	MONTH	% RETURN
Natera (NTRA)	August 2017	52.09%
Leonardo DRS, Inc Common Stock (DRS)	August 2017	45.97%
Centrais Electricas Brasileiras (EBR)	August 2017	30.77%
Celsius (CELH)	August 2017	25.71%
Stellantis (STLA)	August 2017	24.32%
Pure Storage (PSTG)	August 2017	22.85%
Take-Two Interactive Software (TTWO)	August 2017	22.56%
Texas Pacific Land Trust (TPL)	August 2017	21.8%
Centrais Elétricas Brasileiras SA - Eletrobrás (EBR.B)	August 2017	21.32%
Okta (OKTA)	August 2017	21.14%
Pilgrims Pride (PPC)	August 2017	20.89%
Alamos Gold (AGI)	August 2017	17.99%
Illumina (ILMN)	August 2017	17.53%
Arista Networks (ANET)	August 2017	17.1%
Neurocrine Biosciences (NBIX)	August 2017	16.75%
Ralph Lauren Corp Class A (RL)	August 2017	16.52%
Dell Technologies (DELL)	August 2017	16.1%
Teck Resources Ltd Class B (TECK)	August 2017	15.2%
Marvell Technology (MRVL)	August 2017	14.88%
Insulet (PODD)	August 2017	14.74%
ON Semiconductor (ON)	August 2017	13.87%
United States Steel (X)	August 2017	13.38%
Micron Technology (MU)	August 2017	13.29%
Novo Nordisk A-S (NVO)	August 2017	13.28%
Franco-Nevada (FNV)	August 2017	13.1%

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