Abstract: In the present study, the method of collagenase-pepsin prepared cell suspension of human placental villi from early (10～12 weeks) and term (38～40 weeks) gestation cultured in vitro combined with progesterone radioimmunoassay was employed. The results indicated that: 1 In the placenta villi cells from early and term gestation in vitro, both exogenous and endogenous hCG showed a stimulatory effect on progesterone secretion, and the effect was approximately proportional to the concentration of the exogenous hCG added. 2. In the placenta villi cells from term gestation in vitro, after addition of sufficient rabbit antih CG IgG to the culture medium, LHRH-A exhibited no obvious influence on this hCG-independent progesterone secretion. However, in the absence of rabbit anti-hCG IgG in the culture medium, LHRH-A showed a stimulatory action on progesterone secretion probably via its stimulatory effect on hCG secretion which could subsequently increase the progesterone secretion. 3. In the placenta villi cells from early gestation, LHRH-A exhibited an inhibitory effect on both hCG-independent and hCG-dependent progesterone secretion.