In vitro fertilisation after stimulation of the ovulatory cycle has led to successful pregnancy. If more oocytes are recovered than are needed they may be left unfertilised, preserved, or donated to a recipient couple from whom oocytes cannot be obtained. A case of human pregnancy initiated by transfer of a donated embryo fertilised in vitro is reported. The donor was a 42 year old woman with primary infertility from whom six follicles were aspirated after stimulation of the ovulatory cycle. The recipient was a 38 year old infertile woman who had undergone several unsuccessful attempts for artificial insemination from a donor. Five oocytes were recovered from the donor's six follicles, four of which were inseminated with spermatozoa of the donor's husband and the fifth with a frozen sample of semen. Three of the four embryos fertilised by her husband were returned to the donor and the fifth was transferred to the recipient. No pregnancy was recorded in the donor, but pregnancy was confirmed in the recipient, though spontaneous abortion occurred after 10 weeks. This case will give useful information for further study of in vitro fertilisation, but also raises many ethical issues.