Immunosuppression by exogenous corticosteroids has been used to improve the rates of embryo implantation and pregnancy in in-vitro fertilization (IVF) patients who have micromanipulated embryos replaced. The present study was conducted, in a prospective design, to evaluate effects of corticosteroid on the pregnancy rate in IVF/embryo transfer patients who have non-micromanipulated embryos replaced. Infertile women <40 years old with tubal factor were included in this study. Patients were grouped according to the different follicle stimulation protocols, and received various doses of 16 beta-methylprednisolone (0, 16 or 60 mg/day) for 4 days from the day of oocyte retrieval. The mean age, duration of infertility, length of folliculogenesis and serum oestradiol concentrations at the time of human chorionic gonadotrophin (HCG) injection were not significantly different between control and corticosteroid-treated groups of patients. Short-term immunosuppression by 16 beta-methylprednisolone administration did not show any effects on the pregnancy and miscarriage rates in IVF/embryo transfer patients. Also, immunosuppression showed no dose effects in any groups. There was no relationship between the types of follicle stimulation protocols and the effect of 16 beta-methylprednisolone. Therefore, we concluded that short-term immunosuppression by exogenous corticosteroids in IVF/embryo transfer patients who have embryos with intact zona pellucida replaced has neither positive nor negative effects on pregnancy rates.