The distribution of the alpha 1-antitrypsin (Pi) phenotypes and subtypes was investigated in a population sample of 1060 unrelated individuals from Serbia (Yugoslavia). The allele frequencies estimates were: Pi*M1: 0.702; Pi*M2: 0.183; Pi*M3: 0.088; Pi*Z: 0.013, Pi*S: 0.007; Pi*P: 0.004; Pi*F: 0.003. The observed phenotype frequencies differed very significantly from those expected assuming H.W. equilibrium (chi 2 = 49.51, p < 0.0005). The deviation from equilibrium involved the three Pi*M subtypes: an excess of Pi*M1, Pi*M2 and Pi*M3 homozygotes was found, with the corresponding decreased number of M1M2 and M1M3 heterozygotes. The possible significance of this finding is discussed.