113 Greeks living in W. Germany and coming from various parts of Greece and 281 individuals from the Isle of Alonissos (northern Aegean Sea) have been typed for six serum protein polymorphisms, namely haptoglobin, group specific component (Gc), C 3, transferrin subtypes, Gm (1, 2, 3, 5, 13), and Inv (1). The gene frequencies obtained in these two samples are compared with the up to now reported data from other Greek populations. They show a marked genetic heterogeneity with respect to these polymorphisms.