Throat swabs for group A beta-haemolytic streptococci were taken from 120 Coloured children and 126 Indian children at approximately 3-monthly intervals during 1980. The prevalence of positive throat swabs was related to crowding at home as measured by the number of people per bedroom. Coloured homes were much more crowded than Indian homes, but no statistical relationship was found between the number of persons per bedroom and the positivity rates. Both groups of children had high positivity rates in summer (24,4% and 21,3% for Coloureds and Indians respectively) but low rates in spring (4,3% and 3,4% respectively). These positivity rates do not support the provision of primary prophylaxis against acute rheumatic fever for these children.