Fertility potential of 135 patients who had an orchidopexy aged between 2 years 7 months and 15 years 8 months has been evaluated using semen analysis. The patients were divided into several groups taking into consideration the following criteria: (1) unilateral (112 cases) and bilateral (23 cases) orchidopexy; (2) the patient's age at the time of the operation: under 6, between 6 and 10, and over 10 years; (3) position of testes at the time of operation: abdominal, canalicular or inguinal. It has been found that increasing age at the time of unilateral orchidopexy the fraction of patients with normospermia decreases and the average number of spermatozoa both in 1 ml and in the sperm liquid as a whole goes down. In the smaller group of the bilateral orchidopexy patients the differences are not statistically significant. The beneficial effect of early operation is more clearly seen in the sub-groups of patients with the same pre-operative testicular position. Since the fertility potential is higher among the earlier operated patients, orchidopexy performed as early as possible (preferably between 1 and 2 years of age) may bring a chance to improve the results of treatment.