SUmmARY In Lagos 12 755 schoolchildren aged between six and 12 years were screened for evidence of rheumatic heart disease and showed a prevalence rate of 0.03 %. Group C (27.7%) and group G (47 *3 %.) predominated in the throat and in cases of pharyngitis, while group A predominated on the skin. Two hundred and sixty-six cases of pharyngitis were recorded, 70 (26.4%) were positive for 3-haemolytic streptococci. Half of the cases of streptococci were caused by group A 3-haemolytic streptococci while 28.2 % and 21.1 /% were caused by groups C and G respectively. A diversity of serotypes of group A streptococci, which included types 49 and 55, and C and G streptococci were isolated from impetiginous skin lesions. The main point of interest is the association of group C and G streptococci with sore throat and skin infections. The pathogenicity of C and G in such circumstances merits further investigation. The present study also showed that prophylactic benzathine penicillin (Penadur) given to patients with rheumatic heart disease or rheumatic fever had been effective with no recurrent attack of acute rheumatic fever.