Failure to retrieve oocytes during in vitro fertilization (IVF) treatment was recently referred to as the 'empty follicle syndrome.' Data on the possible repetitiveness of this during previous or subsequent IVF attempts is lacking, which limits the understanding of its significance to the involved patients. Of 26 patients who had cycles during which no oocytes were retrieved, 10 were pregnant in the past and 20 had at least one other IVF cycle that yielded oocytes. There was no difference in the frequency of any stimulation protocol among the failure cycles compared with the successful ones. Hormonal response pattern and the number of large follicles observed sonographically did not differ between the two occasions. Fertilization occurred in 70% of the successful cycles and two biochemical pregnancies were recorded. In 13 patients, at least one cycle was canceled because of poor ovarian response, but 9 of these 13 had at least one other successful cycle. We conclude that the so-called empty follicle syndrome cannot be predicted by the pattern of ovarian response and does not predict a reduced fertility potential in future cycles.