A method of controlling the spark lead of an internal combustion engine having at least one cylinder fitted with a spark plug; the method including the steps of: determining a standard spark lead value; determining an engine knock index in the cylinder; calculating a correction factor as a function of the engine knock index; determining a modified spark lead value by applying the correction factor to the standard spark lead value; and controlling the spark plug using the modified spark lead value. The correction factor is calculated by statistically analyzing a number of engine knock indexes to calculate a cumulative distribution; comparing the cumulative distribution with at least one target value; and modifying the current correction factor value as a function of the comparison between the cumulative distribution and the target value.