The distribution of 13 genetic markers (AB0, Rh, ACP, ADA, AK, ESD, GLO, PGD, PGMl, SOD, GC, TF, and PI) were studied in a sample from the Alia population of Sicily, Italy. A total of 34 alleles were detected. In comparison with other Sicilian populations, Alia always appeared genetically distinctive, either in terms of overall genetic diversity or for the number of unique alleles present. The results are consistent with previous studies that show no genetic uniformity within the island. More specifically, the data support the genetic divergence of the eastern and western halves of the island and highlight genetic boundaries that run through Sicily and divide it into three distinct areas. Am. J. Hum. Biol. 14:289–299, 2002. © 2002 Wiley-Liss, Inc.