Serious infection caused by Lancefield group C streptococci is unusual in man. Two unrelated deaths associated with these organisms in a 55 year old woman who died after three days of diarrhoea and vomiting, and in a 65 old man who died after a week of non-specific symptoms, are presented. Post mortem examination showed septicaemia in the former and severe aortic stenosis with widespread septic emboli and probable meningitis in the latter. Lancefield group C streptococci were isolated from both cases. These organisms may be carried asymptomatically and usually cause disease in animals but cases of serious human infection have recently been described, mainly in elderly patients or those with other predisposing factors.