Transferrin subtypes have been determined by isoelectric focussing of sera from 3,787 individuals in selected populations in the Asian, Pacific and Australian area. TfC1and TfC2were present in all populations studied. TfC3 was found to be polymorphic in a few populations only. The highest frequency of TfC2was found in the Soliga (34%), an Indian tribal population, and the lowest TfC2 safrequency was in Australian Aborigines (3%). In Pacific island populations TfC2was found to be variable between 4 and 22%. A new subtype allele, TfC6, was observed at polymorphic frequency in Australian Aborigines.