The somatic karyotypes of the 21 surviving species of the order Crocodilia are presented. The population surveyed totals 71 animals, with representatives of both sexes in 13 species. No karyotypic differences were observed among the multiple specimens within a given species or subspecies. There was no evidence for consistent heteromorphism that might be indicative of a sex-chromosome pair. All chromosomes possessed distinct morphology and were classified as macrochromosomes in the absence of an absolute distinction between macro- and microcbromosomes. The diploid number in this order ranges from 30 to 42; however, the fundamental number (N.F.) shows only 10% variation (56 to 62). Two obvious marker chromosomes were evident – a satellited submetacentric characteristic of alligators and a telocentric with a marked secondary constriction observed in nine species of crocodiles. Evolutionary pathways of karyotype development are discussed from the consideration of both centromeric ‘fusion’ and ‘fission’.