The group we selected and defined certainly had a very poor prognosis. The pregnancy rates achieved were extraordinarily high both in the day 5 transfers and the day 2 transfers. However, the rate of clinical abortions is also high (biochemical pregnancies were ignored). In the meantime, we have also conducted a further pilot study in which G-CSF was administered to patients with a history of multiple unsuccessful IVF treatments or unexplained sterility, who had no KIR defects. The results were very poor, with pregnancy rates currently below 10% per embryo transfer. We conclude from this that the use of G-CSF is an extremely promising additional method of treatment in cases where defects in materno-embryonic implantation communication can be shown. This applies in particular to KIR defects and, in this, particularly to the lack of the three activating receptors as described by Hiby et al. Where such defects were not present, results of G-CSF treatment were disappointing.