Two different electrophoretic variants of PGM2 have been identified in a S. American Indian population sample. The phenotypes are designed PGM2 1–5 (Trio). From family data they appear to represent heterozygous and homozygous combinations of a variant allele, designated PGM25(TRIO). The isozymes produced by PGM25(TRIO) are electrophoretically similar to those determined by the rare PGM25 allele which has been identified in Europeans.