From December 1981 to February 1982, an estimated 22,000 cases of acute hemorrhagic conjunctivitis (AHC) caused by enterovirus type 70 (EV 70) occurred among Samoan and non-Samoan residents of American Samoa. The overall attack rate was estimated to be 68%. Samoans of all ages resident in traditional housing and of large family size were at greatest risk of acquiring AHC, while non-Samoan adults resident in western style housing were at lowest risk. Epidemiologic aspects of AHC acquisition were also different for the Samoan and non-Samoan communities; index cases in Samoan households were frequently young adults, whereas index cases in non-Samoan households were commonly school age children, suggesting a role for school transmission in non-Samoans only. In this outbreak, subclinical AHC was rare; of 50 asymptomatic members of affected households, only 3 had neutralizing antibody to EV 70 (all with titers of 1:10). Investigation documented the highly contagious nature of AHC caused by EV 70, and the ease with which epidemic transmission may develop under conditions of crowding and frequent interpersonal contact.