We compared clinical, microbiological, and prognostic characteristics of infective endocarditis in patients with and without diabetes mellitus. In 1987--1996, 213 patients with definite or possible infective endocarditis were included, of which 39 (18%) had diabetes mellitus. Diabetic patients were older than non-diabetic (median age of 71 vs 65 y, respectively; p =0.04), had more aortic valve and less mitral valve involvement (71% vs 27%, and 21% vs 62%; p = 0.004). There was no significant difference in the frequency of Staphylococcus aureus involvement between the 2 groups (21% in diabetic vs 20% in non-diabetic group; p = ns). On multivariate analysis diabetes mellitus was not found to be an independent factor for mortality. Unlike other infections diabetes mellitus does not significantly affect clinical and microbiological features, and outcome of infective endocarditis.