Karyotypes for 20 species of elopiform and clupeiform fishes, six of which are reported here for the first time, revealed diploid complements ranging from 28-54 chromosomes. Chromosome sets were comprised of entirely uniarmed elements or, more frequently, combinations of uniarmed and small and large biarmed chromosomes. The association of large metacentric-submetacentric chromosomes with a reduction in total chromosome number is consistent with