81 patients who had consulted for infertility, of whom 26 had recurrent spontaneous abortions (RSA), 28 unexplained infertility (UI), and 27 with difficulties for implantation following in vitro fertilization (IVF) were tested by a cross-match for the presence of the partner's lymphocyte antibodies. When the result was negative, leucocyte transfusions were carried out (200 million of the partner's lymphocytes in 3 successive injections at intervals of one month). Positive antipaternal cytotoxic antibodies were found in 81% of cases. There was, however, no benefit in groups of unexplained infertility or implantation difficulties. In the RSA group there was a 50% recurrence of spontaneous abortions.