The urethra and bladder neck act (bladder outflow) together as a variable resistor, controlling the rate of urine outflow from the bladder. During urine storage the resistance is high and when voiding occurs the resistance is low. A pathological increase of resistance may cause retention of urine; resulting in renal damage if sustained. If a high filling resistance cannot be maintained, urinary incontinence can result. Urethral resistance is determined by several factors: the tone of urethral smooth muscle; the activity of associated skeletal muscle (the rhabdosphincter); and basal turgidity provided by mucosal blood flow. This talk will consider advances in understanding the regulation of smooth contraction and relaxation, in particular via autonomic and nitrergic mechanisms as well as the potential role of interstitial cells in regulating muscle tone. In addition the influence of prostatic smooth muscle tone in regulating urethral resistance will be discussed; of importance to men with benign or malignant growth of the prostate gland. Of particular interest is the synergistic interaction between sympathetic and parasympathetic nervous systems in regulating smooth muscle tone. Finally, the control of rhabdosphincter function and its importance to regulating urethral function will be described. Examples will be provided as to the translation of this fundamental knowledge to management of patients with bladder outflow conditions.