Annual incidence of appendicectomy in urban black and white children of 0-14 yr. for 1985-1987 were estimated from hospital data obtained in Potchefstroom and Bloemfontein, also for black children at Baragwanath Hospital, Johannesburg. Rates per 10,000 children remain low for blacks, varying from 0.5, to 1.9: but were high for whites, 21.5 to 39.5. The latter are within the range of rates published in the West. As to diet, for blacks, mean daily fibre has fallen over several years to 10-14 g, similar to that of whites. Because of progressive fibre depletion, a marked rise in appendicectomies in blacks would be expected. The dietary fibre and the hygiene hypotheses afford only partial explanations for the disease's occurrence. Neither explains puzzling epidemiological differences including the recent fall in whites, nor throws light on the nature of precipitating factors.