Based on new material collected in 1983, 1984, and 1985, the genus Pseudoniphargus proves to be distributed in northern Spain from Asturias, in the western part of the Cordillera Cantabrica, to Navarra and Huesca, in the headlands of the Pyrenees; and from coastal Atlantic regions up to the northern border of the Meseta. A total of 13 species are recognized, of which 11 are new. They are not only found in cave waters, but also in springs, hyporheic habitats, and wells. The species are allopatric in distribution; burgensis n. sp., eborarius n. sp., unisexualis Stock, 1980, and spiniferus n. sp. are known from single localities only; jereanus n. sp., gorbeanus n. sp., vasconiensis n. sp., incantatus n. sp., and guernicae n. sp. have more or less small distribution ranges; longicarpus n. sp., semielongatus n. sp., and montanus n. sp. are distributed in the underflows of some adjacent rivers; and finally elongatus Stock, 1980 has a large distribution, particularly in caves. Morphological differences between the species are in general small, characters considered of major diagnostic importance are found in gnathopod 2, coxal plates, basis and claws of pereiopods 5 to 7, uropod 3, and telson.