Viridans streptococcal bacteraemia is frequent in neutropenic patients. 25 neutropenic patients with viridans streptococcal bacteraemia were compared with 64 control patients. Exposure to repeated chemotherapy or cytarabine were independent risk-factors for streptococcal bacteraemia. The use of carboxyureidopenicillins and a stay in laminar-airflow rooms were protective. In a further cohort study of 49 patients, oral streptococci with the same ribotype as blood isolates were recovered from all 7 bacteraemic patients. The oral cavity is a portal of entry for viridans streptococci bacteraemia in neutropenic patients, especially after oral mucosal damage induced by repeated chemotherapy.