Human rotaviruses (HRVs) derived from stools were cultivated to high titres in an established cell line (MA-104) using the rotary culture system. Analysis of the 11 double-stranded RNA segments of the culture-adapted HRVs was carried out by polyacrylamide gel electrophoresis. Tissue culture-adapted HRVs, uncloned or cloned, had the same RNA gel patterns as those of the original HRVs from the individual stool specimens. The migrations of the RNA segments from the culture-adapted HRVs were markedly different from that of the RNA segments from calf rotavirus (Lincoln strain). Considerable heterogeneity in electrophoretic migration of the RNA was found among eight strains of the HRVs grown in cell culture. These results confirmed that viruses isolated from stool specimens were indeed of human origin and were not the result of laboratory contamination with tissue culture-adapted calf rotavirus or other viruses.