The presentation and course of Staphylococcus aureus bacteremia in 27 diabetic patients (18 insulin-dependent) were compared with those in 34 nondiabetic patients. The groups were comparable in age, proportion with pre-existing cardiac valvular disease, community-acquired bacteremia, fever, and leukocytosis. Endocarditis (vegetation or new regurgitant murmur) was present in eight (30 percent) diabetics and four (12 percent) nondiabetics (p = 0.16). A primary focus of infection was present in 67 percent of diabetics and 65 percent of nondiabetics. Among those with a focus, six of 18 diabetics and none of 22 nondiabetics had endocarditis (p less than 0.005). Fifteen of 54 (28 percent) patients who received appropriate antibiotic therapy died. After stratificaton for underlying illness, there was no mortality difference between those with and without endocarditis (three endocarditis deaths versus 1.78 expected), or between those with and without diabetes (four diabetic deaths versus 4.8 expected). Diabetics with staphylococcal bacteremia were more likely than nondiabetics to have endocarditis in the presence of a primary focus. They had no increase in mortality.