We perform a statistical study of the decay times for the recovery phase of the 300 most intense magnetic storms that occurred from 1 January 1957 to 31 December 1998. The Dst index in the decaying stage has been fitted by an exponential function, and a very good correlation has been obtained for most of the storms. Statistically representative values for the decay time (τ) are obtained by averaging the most reliable τ values, which resulted from applying a least squares method to the Dst index time series during every recovery phase. The mean value of τ turned out to be ~14 ¿ 4 hours. We have also found that for very intense storms (Dstmin < -250 nT) the values of τ tend to decrease as the intensity of the storm increases.