Chromosomes from all 17 species of native JamaicanEleutherodactylusas well as introducedE. johnstoneiwere subjected to computer‐assisted analyses. Diploid chromosome numbers of 24, 26, 28, 30 and 32 were found and no two species had identical karyotypes. Karyotypic data were superimposed on a phylogeny derived from allozyme and immunological data in order to assess karyotypic changes that occurred in lineages of JamaicanEleutherodactylus.Chromosome number changes have occurred at least nine times on the island and have involved both fission and fusion mutational events. C‐bands and the sites of secondary constrictions varied and provide very little phylogenetic information. In most instances, karyotypically determined interspecific evolutionary relationships corresponded with the molecular data. The combination of karyological analyses and molecular data clarified lineages which involved convergent chromosome numbers or extremely divergent karyotypes. Karyotypic changes in JamaicanEleutherodactylusare best explained by chromosome fission, fusion, translocations and inversions which arose in isolated demes and have been fixed through inbreeding and genetic drift. Rates of karyotypic evolution among JamaicanEleutherodactylusare much faster than previous published rates for frogs. Karyotypic evolution appears to be dictated by behavioural factors and effective population sizes irrespective of taxonomic groupi