Serogenetic data involving 21 genetic systems were collected from 12 villages on the island of Brač (Yugoslavia) in 1987. Maximum sample size was 709 individuals. The UPGMA dendrogram based on genetic distances was readily interpretable within the contexts of village settlement history, social relationships, and sample size considerations. The gene diversity value (H = 0.3029 ± 0.0119) was both quite high and extremely similar to the average heterozygosity value on the neighboring Pelješac peninsula. Quadratic assignment procedures were used to investigate genetic‐linguistic‐geographic correspondences. Unlike the Pelješac peninsula, where the distance matrix correlations between genetics and linguistics, genetics and geography, and linguistics and geography were all positive and highly statistically significant; on Brač, only the linguistics‐geography correlation achieved statistical significance. Reasons for the differences are sought in the different migrational characteristics of these two population systems, in the complex interaction between evolutionary forces promoting population differentiation (genetic drift) and homogeneity (gene flow), and in known patterns of sociocultural interaction that might have skewed the genetic‐geographic associations on Brač.