A 1-year prospective study of nosocomial bacteraemia was performed at Hvidovre Hospital with special reference to frequency, focus of infection and prognosis. All patients were examined clinically in order to confirm the bacteraemia. In total, 98 hospital-acquired bacteraemias were observed, giving an incidence rate of 0.28%. Bacteraemia due to Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis predominated. The overall mortality was 38%; 65% of the patients with S. aureus bacteraemia died, 25% due to the bacteraemia. The most common types of infection were urinary tract infections and intravenous catheter infections. Fifty-five of the bacteraemias were caused by foreign bodies, mostly urinary catheters and intravenous catheters, and in 14 cases the focus was unknown. The patient population was severely ill patients. We conclude that nosocomial bacteraemia occurs specially in severely ill patients often preceded by indwelling urinary or intravenous catheters. The patients seldom die due to the bacteraemia, but they die with concomitant bacteraemia.