Sixty patients with tubal infertility were stimulated for IVF with a fixed schedule consisting of clomiphene and pure follicle stimulating hormone. They responded with an optimal estradiol increase and 2 to 4 embryos were transferred. Conception cycles (n = 17) could be differentiated from non-conception cycles (n = 43) by serum estradiol, serum progesterone, the serum progesterone/estradiol-ratio and serum LH concentrations. Testosterone, androstenedione and FSH in serum and follicular fluid showed no significant relation to a possible therapy outcome. We conclude from our findings, that, during the peri-implantation period, certain LH patterns followed by an optimal progesterone/estradiol-ratio in the serum support an embryo survival after transfer to the uterus.