The genus Pseudoniphargus, up to now represented in southern Spain by a single species, branchiatus Stock, appears to be widely distributed in the area. Through the present study, based on new collections obtained in 1984 and 1985, a total of 15 species is recognized. The distribution of Pseudoniphargus in the south of Spain seems to coincide with the Betic Cordillera, which is a structural geological entity with important influences of the sea during the Late Cretaceous or Tertiary. Most of the species are allopatric and have very limited distributions. However, in the Guadalquivir basin one species, latipes n. sp., is widely distributed while three local species, vomeratus n. sp., cazorlae n. sp. and illustris n. sp., occur within the range of latipes. The morphological interspecific diversity in general is greater than between the species of northern Spain. The southern species cannot be characterized as a whole by a single character or a set of characters, although some characters (e.g. elongate uropod 3 male, narrow basis of posterior pereiopods) tend to be present more frequently in south Spanish species than in other species of the genus.