Of 2030 consecutive patients with bacteremia, only 102 were free from underlying disorders. 43 were males, and the median age was 66 years. The sources of infection were the urinary tract (in 48% lower respiratory tract (13% endocarditis (7% biliary tract (6% and the meninges (5% The most common pathogens were Escherichia coli (in 45% of patients), Streptococcus pneumoniae (21% Staphylococcus aureus (9% and hemolytic streptococci (9% Overall mortality rate was 13% 4% in patients with urinary tract infection and 19% in patients with other sources. Half of the deaths occurred within 2 days of hospitalization, and 75% of them within 4 days. All patients with septic shock and all patients with meningitis died. Other factors related to mortality were residence in a nursing home, low functional capacity, advanced age, high blood urea nitrogen and creatinine and low albumin, and infections caused by Staphylococcus aureus, Neisseria meningitidis and polymicrobial infections. A protective effect of appropriate antimicrobial antibiotic therapy could not be demonstrated. In conclusion, bacteremic patients with no known underlying disorder and source of their infection other than the urinary tract should be given maximum supportive treatment and should be closely watched.