The aim of our studies was to compare the roles of leptin and ghrelin in the direct control of proliferation, apoptosis, and secretory activity by porcine ovarian cells. In our in vitro experiments, we analyzed the effects of leptin and ghrelin treatments (at 0, 1, 10, or 100ng/mL medium) on the accumulation of proliferation-related peptides (PCNA, cyclin B1, MAP kinase [MAPK]) and apoptosis-associated peptides (Bax, caspase 3, p53), and on progesterone secretion by cultured porcine granulosa cells, using immunocytochemistry, SDS PAGE-Western immunoblotting, and radioimmunoassay (RIA). Leptin stimulated proliferation (PCNA, cyclin B1, MAPK), apoptosis (Bax, p53), and progesterone secretion. Ghrelin promoted proliferation (PCNA, cyclin B1, MAPK) and progesterone secretion but suppressed apoptosis (Bax, caspase 3, p53). These observations suggest that both leptin and ghrelin directly control proliferation, apoptosis, and secretory activity by porcine ovarian cells. At the level of the ovary, in contrast to the hypothalamo-hypophysial system, leptin and ghrelin may have similar action in promoting granulosa cell proliferation and progesterone secretion, but they may be antagonistic to one another (leptin, stimulator; ghrelin, inhibitor) in controlling apoptosis.