Abstract： Objective Urethral function is essential for efficient voiding.This study focused on the function of the external urethral sphincter (EUS) in DM rats. Methods Female SD rats with the weight of 250-275g weight initially were used.DM (n=6) was induced by an i.p.injection of streptozotocin (65 mg/kg) and allowed to progress for 6 to 8 weeks,and age-matched normal rats (n=5) were taken as control.A double lumen catheter was used to simultaneously record isovolumetric bladder pressure and urethral perfusion pressure (UPP) under urethane anesthesia.EUS-EMG(electromyogram) activities were also recorded using fine wired electrodes. Results Blood glucose of all DM rats was>300 mg/dl.High frequency oscillations (HFOs) of UPP were significantly reduced in some diabetic rats, but never in controls.The increased tonic EUS activity in diabetic rats resulted in increased urethral resistance (UPP was 23.5±1.6mmHg in DM rats compared with 7.9±1.8mmHg in controls,P<0.05). Conclusions These results demonstrate that DM induces EUS dysfunctions, decreases urethral relaxation and increases urethral outlet resistance during reflex voiding