In this study, it was aimed to investigate the toxic and teratogenic effects of cyclosporine A and tacrolimus and their combinations with prednisolone using an in vitro rat embryo culture technique. Cyclosporine A (4-40 μg/ml), tacrolimus (1-20 μg/ml) and combinations of these drugs with prednisolone (20 μg/ml) at different concentrations were tested. Cyclosporine A and its combination with prednisolone were determined to have toxic effects on embryonic growth after 10 μg/ml. When used alone, the lowest dose of tacrolimus had embryotoxic effects on the total morphological score and number of somites. It was determined that cyclosporine A caused hematoma at 4 μg/ml and higher doses, and tacrolimus especially at 20 μg/ml caused an open neural tube beside hematoma. It was observed that cyclosporine A at 40 μg/ml dose initiated apoptotic effects at a very low rate, prednisolone increased this effect, tacrolimus led to excessive apoptosis after 15 μg/ml, and this effect did not change with prednisolone supplement. We are of the opinion that the doses should be determined carefully when cyclosporine A and tacrolimus are required to be administered to pregnant women with prednisolone combination, as prednisolone increases the toxic effects of cyclosporine A, and increases teratogenic effects of tacrolimus.