In the Centre for Assisted Reproduction of the Second Gynaecological and Obstetric Clinic, First Medical Faculty, Charles University and General Hospital Prague, during the period from 1993-1997, 900 couples were examined on account of sterility. In 8%, i.e. 72 couples the cause was not elucidated. The female patients were divided into groups by age, parity and period of sterility. In these groups the cumulative conception (CCR) was compared as well as the fecundity per cycle after three months without treatment, after three cycles of intrauterine insemination (IUI) and after three cycles of in vitro fertilization (IVF) or intracytoplasmic sperm injection into the oocyte (ICSI). In the group of patients with sterility shorter than three years, the cumulative conception rate after three months without treatment was 34.8%, after the subsequent three cycles of IUI 27.3% and after three cycles of IVF/ICSI 66.7%. In women with sterility extending over more than three years these results were significantly lower: without treatment CCR was 12.5%, when IUI was used it was 16.1% and after IVF/ICSI 40.5%. There were also marked differences in the age groups. Based on these results the authors elaborated an optimal individual therapeutic pattern. Treatment can be postponed by three months in women under 30 years and those where sterility persists for less than three years. If they do not become pregnant, 3-4 IUI cycles should be attempted. Even women where IUI fails have a fair chance to become pregnant by IVF ET. In women above 30 years with sterility lasting more than three years there the chance that they will become pregnant without treatment is only when secondary sterility is involved. IUI increases the probability of pregnancy in this group only slightly. If during stimulation before IUI more than four follicles grow, it is advisable to convert these cycles to IVF. In women above 39 years the authors recommend IVF or ICSI resp. as the method of first choice.