To examine genetic affinity among Oceanian populations, polymorphisms of exons six and seven of the ABO blood group gene (ABO) were investigated in three populations--Munda town, Paradise village, and Rawaki village--in the New Georgia group of the Solomon Islands. The Munda and Paradise populations consist of Austronesian (AN)-speaking Melanesians; the Rawaki population consists of AN-speaking Micronesians who migrated from the Gilbert Islands to the New Georgia Islands approximately 30 years ago. We recently described the polymorphisms of ABO in three other Oceanian populations--Balopa Islanders (AN-speaking Melanesians), Gidra (non-AN-speaking Melanesians), and Tongans (AN-speaking Polynesians). The results from these six Oceanian populations suggest: (1) the main alleles in Oceanian populations are ABO*A101, ABO*A102, ABO*B101, ABO*O01, and ABO*O02, among which the most predominant is ABO*O01, and (2) there are marked differences in the ABO allele frequency spectrum among Oceanian populations. The different geographical distribution of ABO alleles provides insight into the migration history of AN-speaking populations in Oceania.