Thirty-six infertile patients with primary ovarian failure, who were referred for oocyte (embryo) donation are reported. After substitution therapy with oestradiol valerate (per os) and progesterone (i.m. or per os), endometrial tissue was made receptive for embryonic implantation, although the endometrial biopsies on day 21 demonstrated a certain delay in development (of 1.6-2.4 days). Six patients became pregnant, three of them delivered four healthy babies, one pregnancy is progressing normally and two ended in an early clinical abortion.