The determination of phosphoglucomutase (PGM1) phenotypes was performed by isoelectric focusing on samples from 1678 unrelated individuals from Hessen, Germany. Ten common phenotypes are considered as gene products of four alleles at the PGM1 locus with the following frequencies: PGMa1(1) = 0.6305, PGMa2(1) = 0.1844, PGMa3(1) = 0.1320, and PGMa4(1) = 0.0530. Twenty-two different mating types were observed in 113 families with 202 children. The segregation of the phenotypes in the offspring supports the assumed way of autosomal codominant inheritance. The example of a silent allele (PGM0(1)) as well as a rare variant (PGM7(1)) is reported.