Our trading strategy is inspired from the paper "implied volatility indices as leading indicators of stock index returns?", Giot (2002,). It uses stylized facts observed in stock markets: the so called "leverage effect", the clustering and the mean-reverting behaviour of the implied volatility. Based on S&P100 and VIX data, we show that abnormally high levels of volatility can be used as a trading signals for long traders. A bootstrap procedure confirms the significant returns for the 1986-2003 period.