1-(2,6-Dimethylphenoxy)-2-(3,4-dimethoxyphenylethylamino) propane hydrochloride(DDPH) caused parallel rightward shifts of the phenylephrine(Phe) concentration-contractile response curves and did not suppress the maximal contractile response to Phe (pA2=7.24) in isolated rabbit urinary bladder smooth muscle. DDPH decreased the parameters of cystometry in urethane-anesthetized rats. Thirty minutes after DDPH (25 and 50 mg*kg-1 ig) administration, bladder capacity, voiding pressure, voiding threshold pressure were significantly decreased. With the observation of light-microscope and electron-microscope technique, DDPH (25 and 50 mg*kg-1*d-1 ig for 4 weeks) also inhibited the development of testosterone propionate-induced benign prostatic hyperplasia in rats. The results indicate that DDPH may inhibit benign prostatic hyperplasia and improve the urinary flow.