This study used surnames collected in 12 municipalities of Sulcis, a historic-geographical region located in southwest Sardinia (Italy). An ecological index of similarity was drawn as the main analysis. The distribution of surnames was also used to determine the diversity of municipality populations by using another ecological index. Two municipalities have a high percentage of Genoese surnames and this element reflects a specific history and culture, different from other Sardinian localities. These peculiarities are evident in the topological representation, which graphically emphasizes the links between the populations studied. Two other municipalities can be distinguished from the remaining eight. Above all, historical, socioeconomic, cultural, and geographic considerations are useful in the appropriate interpretation of the results. Am. J. Hum. Biol. 14:391–397, 2002. © 2002 Wiley-Liss, Inc.