While diarrheal disease is a well-recognized problem in children, its impact in the elderly has not been adequately assessed. Among the 4.06 million hospitalizations in 1985 in the McDonnell-Douglas Health Information System database, 98,185 hospitalizations, including 1,130 deaths, had gastroenteritis recorded as a discharge diagnosis. The authors analyzed the 87,181 hospitalizations and 514 deaths for which gastroenteritis was one of the top three diagnoses. Gastroenteritis was among the top three diagnoses in 9% of all hospitalizations of children 1-4 years of age, compared with 1.5% of hospitalizations throughout adulthood (greater than or equal to 20 years). Only 0.05% of hospitalizations involving gastroenteritis were fatal for children younger than 5 years, compared with 3% in individuals 80 years or older. While children aged less than 5 years and adults aged 60 years or more each comprised one-fourth of hospitalizations involving gastroenteritis, the older group represented 85% of diarrheal deaths. Age was the most important risk factor for death subsequent to a hospitalization involving gastroenteritis (odds ratio = 52.6, 95% confidence interval 37.0-76.9 for age greater than or equal to 70 years vs. less than 5 years). Gastroenteritis is a large, underemphasized public health problem among the elderly, among whom its case-fatality ratio is higher than in children.