Urinary tract infections occur more frequently in diabetic patients than in the general population, with a relative risk ranging from 1.5 to 4, depending on the type of infection. The reasons underlying this higher susceptibility have not been established with certainty; urine glucose excression (which could facilitate bacterial urinary proliferation), immunodeficiency, a modified urothelium (resulting in a higher bacterial adhesion), and chronic neurologic bladder dysfunction have been advocated. Clinical presentation, bacterial epidemiology, and treatment of urinary tract infections in diabetic patients are similar to that of the general population. Accordingly, diabetes mellitus has recently been withdrawn from the list of criteria which define an urinary tract infection as complicated. Asymptomatic bacteriuria is particularly frequent in diabetic patients and should be checked routinely as it constitutes an important risk for subsequent symptomatic infection.