The prevalence of bacteriuria as well as bacterial virulence and host factors were studied in 514 diabetic outpatients and 405 nondiabetic controls. The prevalence of bacteriuria was not significantly higher in diabetic women (15/239, 6.3%) than in age-matched nondiabetic women (8/236, 3.4%). In diabetic and nondiabetic men, the prevalence was also similar but lower than in women. E. coli was found in 55% of urine cultures with significant growth from diabetic patients, while in 91% of positive cultures from nondiabetic controls. Most E. coli strains lacked ability of P-fimbriae-mediated adhesion and aerobactin-mediated iron uptake, indicating low bacterial virulence. Long-term metabolic control (HbA1c), prevalence of retinopathy, neuropathy and previous foot ulcers were similar in bacteriuric and nonbacteriuric diabetic patients, matched according to gender, age, and duration of diabetes. Renal function was also similar, though the frequency of proteinuria and elevated blood pressure tended to be higher in the bacteriuric than in the noninfected group. Eight-three percent of the bacteriuric patients reported previous urinary tract infections but only 61% of nonbacteriuric patients (p = 0.07). As compared to non-diabetic women, diabetic women reported significantly more previous urinary tract infections (p < 0.01). In conclusion, the prevalence of bacteriuria in diabetic outpatients was not significantly higher than in non-diabetic outpatients or healthy volunteers. No studied host factor was clearly associated with bacteriuria in diabetic patients, although proteinuria and hypertension tended to be more common. The infecting E. coli strains were of low virulence.