Phenotype and gene frequencies among Atacameño Indians are presented for nine serum protein polymorphisms (Hp, Gc with subtypes, Tf with subtypes, Amy, C3, Bf, PLG) and nine red-cell-enzyme polymorphisms (AcP, PGM1 with subtypes, AK, ADA, 6-PGD, GPT, EsD, GLO). Four systems--Tf, Amy, AK, ADA were found to be monomorphic. In the PGM1 subtypes an extremely high frequency of PGM1a3 could be observed. In two samples a new Gc mutant was identified and classified as Gc1A26. In the EsD system an unusual phenotype was detected in one sample.