The relative frequencies of the Wa (corresponding to serotype P1A), DS-1 (P1B), M37 (P2), and AU-1 (P3) alleles of the VP4 gene from rotaviruses collected from the stools of individuals in Japan between 1982 and 1991 were determined to be 83.1, 15.6, 0, and 1.3%, respectively, by a polymerase chain reaction-based typing assay.