During a period of 3 years in a University Hospital in Israel, 339 episodes of bacteraemia were observed in patients 80 years of age or older, and 658 episodes in patients 60-79 years of age. Patients older than 80 were more often residents of nursing homes, frequently had a history of a cerebrovascular accident, but were less often neutropenic. Twenty-four per cent of bacteraemia episodes in the very old were hospital acquired compared with 40% in the old patients. The most common source of bacteraemia was the urinary tract, 50% of episodes in the very old, and 34% of episodes in the old.The percentage of episodes in which anaerobic bacteria were isolated was 5% in the very old and 1% in the old, and the difference was significant when corrected for the sources of bacteraemia. All cases of community-acquired bacterial endocarditis in patients of 80 or over were caused by pathogens originating from the gut.Thirty-five per cent of patients of 80 and over and 30% of patients aged 60-79 years died during hospitalization. Fatality was not associated with advanced age in the very old. Factors significantly and independently associated with fatality in both groups were a hospital-acquired infection, shock, low serum albumin, renal dysfunction and inappropriate antibiotic treatment.