The G and P types of 2,912 rotavirus-positive fecal specimens collected from eight geographical areas of the United Kingdom between 1995 and 1998 were determined by reverse transcription-PCR. Although 15 different G-P combinations were identified, G1P[8], G2P[4], G3P[8], and G4P[8] strains constituted 95% of all the rotaviruses typed. Other genotypes included G9P[6] and G9P[8], which were first identified in the United Kingdom in 1995, or other uncommon G and/or P types of strains that may have had an animal origin. Unusual combinations of G1 or G4 with P[4] and G2 with P[8] which may have arisen by reassortment between human strains were also identified. G1P[8] was the genotype most frequently found (57 to 87%) in each season, followed by G2P[4] in the 1995-1996 (18%) and 1997-1998 (16%) seasons, although the incidence of infection with this virus decreased significantly to 2% during the 1996-1997 season. Significant differences were seen in the distributions of G1P[8], G2P[4], and G9P[8] strains between children and adults, in the temporal distributions of G4P[8] and G9P[8] strains within a season, and in the geographical distributions of each of the four most common genotypes from one season to the next.