The incidence of bacteraemia and fungaemia was determined in 29 adults with cystic fibrosis (CF) during 50 consecutive admissions to hospital for management of infective exacerbations of pulmonary disease. Blood was drawn for aerobic, anaerobic and fungal cultures from all patients who were febrile on admission or who became febrile during treatment. The population included eight patients who had indwelling venous access systems in situ. The overall incidence of positive blood cultures in febrile patients was 3.5% [95% confidence interval (C.I.), 1-6%]. We recorded one case of Pseudomonas aeruginosa bacteraemia and two cases of Candida albicans fungaemia. The patient with P. aeruginosa bacteraemia died 5 days after isolation of the organism from her blood. The two patients with C. albicans bacteraemia had totally implantable venous access systems (TIVAS) in situ and both recovered following appropriate therapy. These observations suggest that bacteraemia is rare in patients with CF but that there is a significant risk of fungaemia in a susceptible minority. The implications of these findings, as they relate to management of infections and care of indwelling catheters in such patients, are discussed.