Background: All patients who entered our assisted reproductive technology (ART) program during last 7 years were analyzed in order to compare the outcome of in vitro fertilization (IVF) cycles after early cleavage stage embryo transfers and blastocyst transfers. Results: Among 6098 included patients, 292 (4.8 %) were poor, 1450 (23.8 %) low and 4356 (71.4 %) good responders. Total fertilization failure was observed in 5.7 % (350/6098) of all cycles. Among the cycles with fertilization, embryo transfer on day 3 was planned in 1940 (33.9 %) cycles and blastocyst transfer on day 5 in 3788 (66.1 %) cycles. Transfer was cancelled in 6.8 % (394/5748) of cycles, more frequently after embryo culturing in vitro for 5 than for 3 days (7.8 % vs. 6.1 %). However, more women delivered after blastocyst transfer compared to early stage embryo transfers in low (9.5 % vs. 6.1 %), poor (23.7 % vs. 15.2 %) and normal (39.9 % vs. 17.3 %) responders. Multiple delivery rate was also higher after blastocyst rather then after early embryo transfers in low (24.3 % vs. 13.3 %) and normal (29.4 % vs. 24.6 %) responders. Conclusions: The transfer of blastocyst stage embryos increases the success rate of ART procedures in all patients. To avoid multiple pregnancies, single blastocyst transfer is recommended.