Immunotherapy (immunization twice at 5 and 7 weeks of gestation with X-irradiated 200ml total blood or 1-200 x 10(6) mononuclear cells from the husband) was performed on 200 women without autoimmune abnormalities but experiencing habitual abortions of unknown causes between August, 1982 and September, 1990. One hundred fifty-seven babies were eventually born alive. The oldest offspring was 7 yrs 4 mos in August, 1991. We investigated the safety of the immunotherapy in terms of its effects on the women, conditions during pregnancy/labor and conducted long-term follow-up on offspring. Among 190 women whose pregnancy terminated by September, 1990, 152 cases gave birth, including 5 sets of twins. The successful rate was 80.0%. There were no complications among the 200 cases, only 2 small-for-dates babies (1.3%) among 157 babies born alive, and 1 baby born dead in the 3rd trimester, but that was not directly related with immunotherapy. Tsumori-Inage Infant Mental Development Test found no abnormalities (3 yrs and over). At 3 yrs, and only 1 child scored under the mean--2 standard deviation in height and weight. Thus, the safety of the immunotherapy was confirmed by long-term follow-up of both mother and child in which no notable complications resulting from immunotherapy with the husband's X-irradiated cells could be found.