Abstract: Serum levels of progesterone were determined after vaginal and intramuscular administration of progesterone 50 mg to eight women (27～42 years of age). Subjects were injected in the follicular phase of the menstrual cycle, i.e. on the 9～13 th day of the menstrual cycle. Blood samples were collected at 0, 1, 1.5, 2, 3, 5, 7, 12 and 24h after administration and serum concentration of progesterone were determined by RIA.Pharmacokinetic parameters were calculated by both one-compartment open model and statistical moment non-model analysis. Their absorption rate constant, elimination rate constant and time to peak (Tmax) were approximate, which were 0.50～0.66, 0.06～0.05 and 5 h respectively. The mean residence time of drug in the body (MRT) of suppository was 21h and that of injection was 20 h. Area under the serum concentration-time curve for suppository was 0.27～0.28 times that of injection (P<0.01).