The karyotypes of 47 Spanish acridold grasshoppers have been analyzed by means of C-banding in both mitotic and meiotic cells. The most frequent location of C-heterochromatin occurs in centromeric and telomeric regions whereas interstitial C-bands are very scarce. No clear relationship between similarities in C-banding patterns and taxonomic proximity has been found. Negatively heteropycnotic regions are described; their uniform location and distribution suggest that they could represent a functional chromosome structure as nucleolar organizers.