It was shown in some randomized controlled trials that clinical pregnancy rate and delivery rate are higher after vitrified/thawed embryo transfer in compare to fresh embryo transfer after ovarian stimulation. In order to improve pregnancy rate the concept of segmentation of IVF treatment and frozen/thawed embryo transfer was supposed not only for patients with high risk of OHSS but for all IVF/ICSI patients. Objective — to compare clinical and ongoing pregnancy rates after single blastocyst transfer in fresh IVF/ICSI cycle and after vitrified blastocyst transfer in natural cycle. Design: Retrospective cohort study. Material and methods. Group I — fresh single embryo transfers in 122 patients at age under 39 years who had ovarian stimulation with menotropin and GnRH antagonist; group II — frozen embryo transfers in 148 women at age under 39 years who falied to conceive after fresh embryo transfer or had transfer cancellation due to  risk of OHSS. Results. In group I, 122 embryo transfers resulted in 53 clinical pregnancies, of these 3 (5.3%) miscarriages and 2 (3.8%) twins. In group II, 148 embryo transfers resulted in 69 pregnancies, of these 8 (11.6%) resulted in miscarriage, 1 (1.4%) was ectopic and and 1 (1,4%) twins. The clinical and ongoing pregnancy rates didn’t differ between the groups (43,4 and 40,9% versus 46,6 and 40,5% respectively). Conclusion. In spite of very high efficacy of vitrification and frozen/thawed blastocyst transfer where is no evidence of advantage of «freeze all» strategy for routine IVF practice.