In 1 year there were 135 episodes of septicaemia in a large referral hospital serving a population of 400,000 people. Of these, 52 were hospital-acquired giving a nosocomial septicaemia rate of 2.08 per 1000 admissions. The mortality rate rose with the number of antibiotics used; from 15% in those receiving one drug to 50% in those receiving three. A wide variety of organisms were encountered, the largest group being Staphylococcus aureus, 12 episodes; and Escherichia coli, nine episodes. Staphylococcus epidermis was pathogenic in seven patients with one death. A review of possible aetiological factors showed that 28 episodes occurred postoperatively with surgery considered directly responsible in 20. Intravenous cannulae were in place in 39 patients at the time of development of infection; they were causal in at least five; with two deaths. Urinary catheters were in situ in 14 patients and causal in at least six, with two deaths. Immunosuppression by drugs carried a worse prognosis than when infection occurred in patients with immunosuppressive disease.