A total of 637 individuals from the rural village of Keneba in The Gambia, West Africa, have been typed for red cell PGM using isoelectric focusing (pH 5--7) in polyacrylamide gels. Eight different phenotypes have been detected. The frequency of the four alleles at the PGM1 locus was found to be PGM1+(1) 0.795, PGM1-(1) 0.053, PGM2+(1) 0.133, AND PGM2-(1) 0.019. A study of the PGM phenotypes in 89 families confirmed the simple Mendelian codominant inheritance of the four alleles. Comparative population data suggest that red cell PGM typing by isoelectric focusing might prove to be a useful genetic marker in anthropological studies.