The modern West Indian island of Hispaniola is in actuality a fusion of two formerly separate islands, each of which presumably supported a distinctive herpetofauna. With the union of these two paleoislands, there has been extensive to small interchange of these faunas; the purpose of the present paper is to analyze the degrees of similarity and difference between the two primal herpetofaunas. A brief sketch of the geography of Hispaniola is given. This is in turn followed by discussions of the 179 native species of amphibians and reptiles of Hispaniola, cataloguing them into six categories: 1) islandwide species; 2) north island species; 3) south island species; 4) north island species that have invaded the south island; 5) south island species that have invaded the north island; 6) species whose original distributions are uncertain. Comparisons are made, as far as success is concerned, between the invaders of the two islands, as well as between the basic faunas of these islands. The south island has by far the greater number of species (116) than the north island (85), despite the fact that the south island comprises about one-eight of the total area of Hispaniola. The herpetofauna of the major Hispaniolan satellitle island, Ile de la Gonâve, is also analyzed. Its herpetofauna is shown to have had a double origin (from both north and south islands), but the total number of species derived from these two independent sources is less than the number of Gonâve species that are islandwide on the Hispaniolan main island.