Leukocyte lysates obtained from blood specimens of individuals from Central and Western Pyrenean groups (Barèges and Basques) and from the population of Toulouse city have been typed for PGMa1 isozymes using isoelectric focusing (pH range: 3–9.5) in polyacrylamide gels. The determination of usual PGM1 phenotypes was simultaneously performed on red cells by starch gel electrophoresis. Significant differences were found between the three communities. In Barèges samples only 6 of the 10 phenotypes known at PGMa1 locus have been observed. In the same group, 36 mating types were studied in distinct families. The segregation on the phenotypes is in agreement with the codominant inheritance of the alleles. In Basques the gene frequencies showed intermediate values between Toulouse and Barèges. PGMa21 reaches a higher frequency in the latter community (0.306). In the Toulouse population sample the results are comparable with those previously published in western Europ