An epidemic of diarrhoea with two distinct waves affected a village of 1375 people in southern India in 1983. The first wave of the epidemic, from the last week of December 1982, had a sharp peak in January 1983 and was over by March. Echovirus type 11 was isolated from patients, who also had a serum antibody response to the virus. During the second wave of the epidemic, from May to September 1983, the clinical features were different and Shigella flexneri was isolated without significant viral isolates. Infection during the first wave did not protect from the second wave. Virus isolation was in human intestinal tumour-derived differentiated epithelial cell lines; such cell lines may be useful for the isolation and identification of enteroviruses in clinical samples.