Between September 1983 and September 1984, 118 cases of hepatitis A were reported from Caddo County, Oklahoma. No common source was identified, and the epidemic curve suggested person-to-person transmission. In July 1984, enhanced control measures were implemented; these consisted of improvements in surveillance, standardization of case investigation, an expanded, although targeted, use of immune globulin, and a public awareness campaign. Control measures resulted in a decrease in the delay between onset of symptoms and case report (from 12 days to 4 days), an increase in the percentage of patients with confirmed cases interviewed (from 77% to 100%), an increase in the percentage of patients reporting contact with a previous case (from 39% to 72%), and an increase in the average number of household-like contacts per case (from seven to 27). Within two incubation periods of the implementation of enhanced controls, the outbreak ended. These data indicate that community-wide outbreaks of hepatitis A can be stopped with an intensive epidemiologic approach, coupled with the expanded and targeted use of immune globulin.