A taxonomic and biogeographic study of the Pyrenean Leuctridae is presented. Keys for males and females of 32 Leuctridaespecies are given.The male of Pachyleuctra bertrandi Aubert, 1952 is described completely for the first time ; P. ribauti Despax, 1929 is restoredas a valid species ; Leuctra ariega Pardo & Vinçon, 1995, L. garumna Vinçon & Ravizza, 1996 and L. prima Kempnyi,1899 are new for the Iberian Peninsula ; L. espanoli Aubert, 1956 is new for the French Fauna.