The effects of progesterone on the urinary tract are not thoroughly discussed in the literature except with respect to hydronephrosis of pregnancy. This article is a comprehensive review of the effects of progestational agents on the ureter, bladder and urethra and the possible clinical uses of this hormone. From the data in the literature, it appears that progesterone brings about relaxation of smooth muscle in the urinary system, which may be important clinically in managing menopausal women on hormone replacement, as well as younger women using oral contraception.