We identify the pluviometric Sahel by setting the northern limit at the isohyet of 150 mm/year from the wettest five-year period and the southern limit at the isohyet of 850 mm/year from the driest five-year period. In this way, starting from Giri's (1983) extended definition (the actual Sahel and the transitional zone towards the Sudanese climate), we have identified the maximum extension reached, under different rainfall conditions, by the Sahel in the period considered. This is the maximum expansion of the Sahelian region in the alternation of wet and dry conditions.