Rotavirus-positive specimens were recovered from 143 Afrikander calves on two farms in the northeastern Cape of South Africa during late 1988 and 1989. The rotavirus strains were analyzed by polyacrylamide gel electrophoresis of the RNA genome, and four rotavirus RNA electrophoretypes, each with a long profile, were identified. A distinct RNA profile was identified on the farms during 1988, but by early 1989, two patterns existed, one unique to each farm. Over the next 8 months a new electrophoretic pattern emerged on one farm, whereas the pattern on the other farm remained unchanged. The rotavirus subgroup I antigen was detected in all specimens examined with subgroup- specific monoclonal antibodies. Non-group A rotaviruses were not identified by RNA genome analysis of 82 specimens from calves with diarrhea negative for group A rotaviruses by an enzyme-linked immunosorbent assay.