We examine how profitability of long?short arbitrage strategies based on anomalies is affected after adjustment for two shorting costs: implicit cost due to unavailability of stocks in the short-leg to sell short and loan fee actually paid to stock lenders. The combined shorting cost amounts to almost 40 percent of gross long?short arbitrage raw returns over the sample period from January 2006 to December 2017. After adjustment for these shorting costs, long?short arbitrage profits are thus reduced by almost 40 percent. Even after adjustment for risk, the proportion of shorting costs is also substantial. If other trade-related transaction costs are considered, long?short arbitrage profits would be reduced further. Our results cast doubt on the profitability of long-short arbitrage strategies based on anomalies.