A survey of rotavirus infection in infants and young children with acute diarrhoea was undertaken in Zaria, northern Nigeria during 1997 and 1998. In total, 375 faecal specimens were collected from children aged between 1 and 60 months and 122 specimens from age-matched control children without diarrhoea. Fourteen specimens were collected from neonates in the University Teaching Hospital. Rotavirus antigen was detected in 61 diarrhoeal and four control specimens; four neonates were shedding rotavirus. Polyacrylamide gel electrophoresis of the viral genome showed the presence of five strains of rotavirus with long RNA electropherotypes and one short pattern. The rotavirus VP6 subgroup was determined by monoclonal antibodies specific ELISA and showed that subgroup II strains predominated (72 vs. 9.8 per cent), while eight strains could not be subgrouped and three did not react at all. Examination of the VP7 serotype showed G1 and G3 strains circulating at similar levels (29 and 25 per cent), but no serotype G2 nor G4 strains were identified. G1/G3 'mosaic' virus strains circulated commonly (10 per cent).