Pairs trading is a popular dollar-neutral trading strategy. This article, using the components of the S&P 500 index, explores the performance of a pairs trading system based on various pairs selection methods. Whereas large empirical applications in the literature focus on the distance method, this article also deals with well-known statistical and econometric techniques such as stationarity and cointegration which make the trading system much more demanding from a computational point of view. Trades are initiated when stocks deviate from their equilibrium. Our results confirm, after controlling for risk and transaction costs, that the distance method generates insignificant excess returns. While a pairs selection following the stationarity criterion leads to a weak performance, this article reveals that cointegration provides a high, stable and robust return.