Electropherotypes of human rotavirus (HRV) isolated from Hong Kong and Guangzhou were compared to study the transmission of HRV between the cities. Forty-one electropherotypes were identified from 418 hospitalized patients with HRV infection at the Queen Mary Hospital, and 22 were detected from 66 outpatients in community clinics at a separate area in Hong Kong. Nineteen electropherotypes were detected in 370 hospitalized cases of HRV infection from seven hospitals in Guangzhou. Results showed that HRV electropherotypes appeared to circulate freely within each area, yet the HRV population between the two cities remained different. Six electropherotypes were common to both cities. Three of these were predominant types found in Guangzhou and later detected in Hong Kong. One of these was found to cause an outbreak in Hong Kong. Of the remaining three electropherotypes, two were detected in both cities simultaneously, whereas one was first detected in Hong Kong.