The karyotypes were studied of fifty-three Spanish Caraboidea species belonging to the following families: Trechidae (3 species), Bembidiidae (48), Pogonidae (1) and Harpalidae (1). Differences in the shape of the largest pair of autosomes (A pair) and the Y-chromosome are frequent among closely related species. The chromosomes of these species have a peculiar centromeric region weakly constricted and surrounded by conspicuous heterochromatic blocks. Eight species have a heteromorphic A pair, probably due to differences in the length of the nucleolar organizer. Species of the first three families either have a male karyotype of 24 chromosomes, or one derived from it, while the only species of the fourth family has a male karyotype of 39 chromosomes derived from the basic karyotype of the Harpalidae, 2n=37.