Seventy five children with acute rheumatic fever (ARF) were hospitalized on Oahu from 1984 to 1988. The annual incidence rate was 9.5 (all rates are per 100,000 children per year). The first attack and recurrent attack rates were 7.9 and 1.6. Polyarthritis occurred in 84%, chorea in 7%, and carditis in 32%. Mitral insufficiency was the most common valvular lesion (88%). Hawaiians/part Hawaiians and Samoans had the highest incidence rates (relative risk 3 and 56, respectively). Polynesian children were 84 times more likely to develop carditis. Five hundred thirty nine ARF cases were hospitalized on Oahu, 1966 to 1974 and from 1976 to 1988. The annual incidence rate of ARF on Oahu has remained fairly constant at about 12.4. The incidence rates in all ethnic groups have decreased except in Samoan children.