[en] We developed a successful bone marrow transplant protocol in MHC-inbred miniature swine (MS). Three groups of MS were studied: irradiation controls, autologous bone marrow transplants and SLA matched bone marrow allografts. One day prior to irradiation, all animals underwent Hickman catheter placement via the external jugular vein. Bone marrow was harvested by direct mechanical removal of marrow from four long bones in Groups 2 and 3 one day prior to irradiation. All animals received 900 rads of midline body radiation from a Cobalt-60 source, were treated 1 g of cephalothin IV bid from day 1 to 14, 20 mg of genetamicin IV bid, from day 4 through 14 and 250 to 350 ml of fresh, irradiated whole blood from blood group identical donors on days 7, 11 and 14. Bone marrow was filtered, washed, stored overnight at 4 C and reinfused one to six hr after irradiation. Engraftment was defined by return of the peripheral WBC to 1000/mm³. All six animals in Group 1 died of aplasia between days 7 and 12. Marrow engrafted in eight of 12 animals in Group 2 and 7 of 10 animals in Group 3. This model provides a means to study the biological characteristics of bone marrow transplantation in immunologically well characterized large animals and should prove useful as a model for bone marrow transplants in man