In the present study we tried to analyse data obtained on the occasion of an in vitro fertilization programme at the department of obstetrics and gynecology of the University of Kiel, to extract some of the important factors, because their positive or negative influence on the success of extracorporal insemination, embryo transfer and implantation has not been clearely defined till now and to value their concern. Between July 1982 and February 1983 105 sterile patients with ovulatory menstrual cycles have been treated by the technique of in vitro fertilization and embryo transfer, successively. Follicular growth was stimulated by 150 mg clomiphen daily from 3rd to 7th day and application of 225 IU hMG on 6th, 8th and 10th day. Finally ovulation was timed 36 hours before follicular puncture by 5000 IU hCG. In 24 per cent endogenous LH peak could be observed. In 86 per cent of the 80 patients exactly timed one oocyte was to be found minimally. In 68 per cent of these patients after all an embryo transfer was done (24 times one embryo, 13 times two, 9 times three and once four embryos). 89% of the embryos have been transfered as 4-or 8-cell stage, only 11 per cent as two cell stage. Transfer took place 48 to 50 hours following insemination. There was no correlation between the maturity classified morphologically of the oocytes and the diameter of their follicles. The speed of development of the embryos was not correlated with the size of their follicles. too. In 60-70 per cent of all cases, in which an embryo transfer was possible, husbands had normal spermiogram. The percentage of unfertilised oocytes following insemination using non-optimal sperma was increased in all types of cycles, additionally there was a reduction of the developing speed of resulting embryos. Doubtless two the four pregnancies resulted after insemination using sperma of less quality. The conjugation rate is said to be not correlated directly with the exactness of timing of the application of hCG with reference to follicular maturity, but in all pregnancies hCG was injected simultaneously with the peak of estradiol.