About 3,500 subjects from Italy and Czechoslovakia have been analyzed by acid starch gel electrophoresis for the subtyping of PGM1 polymorphism. The Italian sample included three different subgroups, from Northern, Central and Southern Italy. The allele frequencies found in the three groups do not differ significantly from each other; the observed values in the pooled sample are: PGM11S = 0.594, PGM11F = 0.118, PGM12S = 0.231, PGM12F = 0.057. In the Czechoslovakian group, which differs significantly from the Italian population, the following allele frequencies were found: PGM11S = 0.639, PGM11F = 0.118, PGM21S = 0.180, PGM21F = 0.063. The analysis of 217 families did not show any exception to Mendelian inheritance of the patterns.