Haptoglobin (Hp) subtypes have been determined in the Japanese population by polyacrylamide gel isoelectric focusing followed by immunoblotting and by two-dimensional polyacrylamide gel electrophoresis. In the present study, neuraminidase-treated plasma samples were used for subtyping of Hp, without prior purification. These samples were obtained from 372 unrelated healthy donors. Allelic frequencies were: Hp*1F = 0.0014; Hp*1S = 0.2688; Hp*2FF = 0.0000; Hp*2FS = 0.7284, and Hp*2SS = 0.0014. The phenotypic distribution was in good accordance with the Hardy-Weinberg equilibrium.