Bladder and urethral function was studied in 52 patients with multiple sclerosis using gas-cystometry combined with sphincter electromyography. 96% of the patients showed abnormalities of either detrusor or sphincter function. The abnormal patterns discovered indicated demyelinating lesions in the corticospinal as well as in the reticulospinal tract. Urgency and urge-incontinence were the predominant symptoms, whereas no signs of involvement of the upper urinary tract found. The use of gas-cystometry provides a fast and differentiated method for assessment of the detrusor function.