["To evaluate the severity of penile deformity and penile blood flow variables in men with Peyronie's disease (PD) and diabetes mellitus (DM), and those with no risk factors.", "Men with PD and DM (59 men, group 1) and those with no risk factors (109, group 2) were compared for penile blood flow variables, severity of penile deformity, patient's age, duration of PD, the presence of pain on erection, and the degree of erectile dysfunction (ED). The men were evaluated with penile duplex Doppler ultrasonography and were categorized into specific vascular groups, using established criteria. Penile curvature was objectively measured and stratified according to the Kelâmi classification. Results were compared using Student's t-test.", 'Men with PD and DM (group 1) were significantly older than those in group 2. The duration of disease was significantly longer in group 1 than in group 2 (median 24 vs 12 months). The mean degree of penile deformity in group 1 was significantly higher than in group 2 (45.2 degrees vs 30.2 degrees). The rate of severe penile curvature (>60 degrees ) was more frequent in group 1 (27.1% vs 5.5%). Pain on erection was significantly higher in group 2 (39.7% vs 25.5%), whereas the rate of ED was more common in group 1 (81% vs 47%). Group 1 had poorer peak-systolic velocity values and significantly higher rates of arterial insufficiency and mixed vascular disease. Nonvascular causes were twice as common in group 2 than in group 1.'] Is diabetes mellitus associated with severe Peyronie 's disease?