In 1984-1985, prevalences of appendectomy in inter-ethnic series of South African school pupils of 16-18 yr were: rural blacks, 0.5%; urban blacks, 1.0%; Indians, 2.6%; coloreds (Eur-African-Malay), 2.2%; Afrikaans whites, 13.4%; and English whites, 9.9%. Corresponding respective annual incidences per 1000 pupils of 10-19 yr were: 0.3, 0.6, 1.9, 1.7, 9.8, and 7.8. Thus, appendectomy is rare or infrequent in all except the white populations. Peak occurrence was postpubertal. There was no consistent sex bias. Dietarily, mean daily fiber intake was relatively low in all groups, 17.9-26.1 g. While the percentage of energy from fat intake was low in blacks, 16.3-22.3%, it was much higher in the other populations, 32.7-39.5%. Clearly, factors other than diet are involved in regulating frequency of appendectomy. While mortality is negligible and morbidity slight, elucidation of causation and prevention of the disease is desirable since subsequently appendectomy patients are at greater than average risk to certain cancers.