Here, we describe our use of the Lagrangian 3-D FLEXPART model to investigate the variation in sources of moisture related to the drier and wetter conditions of the different regions that surround the Mediterranean Basin. We carried out seasonal analyses for the period from March 2000 to February 2005, and identified those years with the highest and lowest rates of precipitation by season, averaged over eight different continental regions. The variation in specific humidity along the 10-day backward trajectories of the particles identified over the target areas was tracked for the selected period, and the characteristics of the moisture sources were then compared between wetter and drier conditions by season. Although they only represented a relatively short period, the results suggest that in most of the years chosen, the moisture sources were more extensive and/or more intense during wetter periods. The contribution of the north Atlantic as a source of moisture is apparent for the Iberian Peninsula, for France and for Central North Africa. Otherwise, the Mediterranean Sea is the predominant source for Eastern North Africa, and for the Italian and Balkan Peninsulas. Local sources provide moisture for the Eastern Mediterranean and Western North Africa.