Vegetable oils that are solid at room temperature are called vegetable fats. A study was conducted in western Slovakia to determine possible effect of used vegetable fats (100 µl/ml) and palm fats (100 µl/ml) after cooking in restaurants on secretion activity of steroid hormone progesterone and 17 β-estradiol on porcine ovarian granulosa cells in vitro. Progesterone and estradiol are essential for normal ovarian cycles and contribute to regulation of ovarian follicular development and remodeling. Release of these hormones by ovarian granulosa cells of Slovakian White gilts was detected by Enzyme Linked Immunosorbent Assay. Experimental results indicated that administration of used vegetable fats and palm fats significantly (P≤0.05) lowered the release of progesterone by porcine ovarian granulosa cells in comparison to control although no such difference was noted in case of estradiol production. Obtained data suggest that used vegetable fats and palm fats may influence steroidogenesis in animals.