We determined the incidence of bacteremia and associated mortality in diabetic and nondiabetic patients in the four major hospitals of one metropolitan area over the 5-yr period 1977–1981. Mortality rates, based on episodes of bacteremia, were similar in diabetic and nondiabetic patients in most instances. Diabetic patients experienced lower mortality rates from Enterobacteriaceae bacteremia compared with nondiabetic patients; this finding was explained by a greater tendency for diabetic patients to have Escherichia coli bacteremia due to community-acquired urinary tract infection. However, the incidence of bacteremia due to all microorganisms was increased twofold in diabetic patients and the incidence of Enterobacteriaceae bacteremia was increased threefold. Because of their increased incidence of bacteremia, diabetic patients in this population were nearly twice as likely to die as a result of bacteremia compared with nondiabetic patients. Thus, the frequent occurrence of bacteremia among patients with diabetes mellitus represents a significant problem.