Gilts reproductive efficiency is one of the primary factors of successful piglets' production. This performance, among other things, is expresses by the number of pregnant gilts, with desirable genetic traits, body weight and age, sexual maturity status, and general good health, provided for the replacement of sows in primary herd. This goal is very difficult to achieve in practical conditions. The main reason is occurrence of prolonged preinsemination anoestrus (oestrus was not detected even after 8 months of age). This paper review the occurrence of prolonged preinsemination anoestrus, based on the results of our and study of other authors. All studies consistently show that, in most of these gilts, pubertal cyclic ovarian activity were established, that silent oestrus occurred in only 4% of the cyclic gilts, and that this problem can be solved by applying appropriate technologies for oestrus detection, and by treatment with adequate hormonal preparations.