OBJECTIVE: The study was focused on comparison of efficiency, safety and tolerance of vaginal use of micronized progesterone in preparations Utrogestan and Crinone 8%. DESIGN: Prospective randomized study. SETTING: Department of Gynecology and Obstetric, University Hospital, Olomouc, Faculty of Medicine and Dentistry, Palacky University, Olomouc. MATERIAL AND METHODOLOGY: Into a prospective randomized study was, after calculation of 80% of the power of the study, α = 0,05, included 111 women in age between 18-40 with a basal value FSH < 10 IU/l and a normal finding in uteral cavity. After evaluation of efficiency of both preparations there was selected a fertilization rate, an implantation rate, a pregnancy rate and a take-home baby rate. Comparison of tolerance was made from evaluation of 21 parameters which were obtained through a questionnaire. RESULTS: There were not been proven any significant differences in efficiency between both preparations. Crinone 8% was in patients better tolerated. CONCLUSION: Luteal support within the IVF/ICSI-ET remains an integral part of the treatment. According to the outcomes of the study it seems to be more suitable to use a vaginal gel for the luteal support with micronized progesterone.