Twenty-two nulli- all primipara who had had previous repeated spontaneous abortions and who did not have anti-HLA antibodies for the partner, received immunological treatment consisting of a single transfusion of the partner's lymphocytes in the third week of pregnancy, and giving natural progesterone supplements after the kinetic of Beta-HCG in the plasma had been assessed. The number of pregnancies which went to terme (94% success) was significantly better than those obtained in our first protocol which was to give one to three transfusions of the partner's lymphocytes before the pregnancy started (58% success rare after 24 treatments). Apart from obtaining much better results the second protocol made it possible to avoid giving a significant number of useless transfusions (22% of pre-conceptual transfusions were not followed by a pregnancy at all).