From September 1976 through March 1978, we investigated 11 outbreaks of non-B viral hepatitis associated with Louisiana day-care centers. The outbreaks included 168 cases, most of which were erroneously considered "sporadic" cases of non-B viral hepatitis prior to the investigations. Thirteen percent of all non-B viral hepatitis cases reported in the New Orleans metropolitan area during 1977 were associated with one of the outbreaks. Most of the cases in each outbreak and 85% overall were in older, usually adult, contacts of children attending the day-care centers. Within the household, parents appeared to be at greatest risk, particularly those who had 1- to 2-year-old children in the day-care center. Day-care center outbreaks of non-B hepatitis are easily overlooked and may be more widespread than is currently appreciated.