Autochthonous human samples of the three westernmost islands of the Canarian Archipelago, La Palma, Gomera, and Hierro, have been analyzed for eight red cell polymorphic enzymes. Only a small intra and inter-insular differentiation exists among these three islands. However, a marked heterogeneity is found when all seven islands of the Archipelago are compared by Nei's genetic distances [1972]. Nevertheless, there is no correlation between genetic and geographic distances. Historical factors could explain the frequency similarities of some distant islands. The rare variant GD*A+Negroid allele, and the endemic GD*Gc allele, previously found in other islands, have also been detected in this survey.