Seven patients with hematologic malignancy refractory to conventional therapy were treated with 1000 rads midpoint tissue dose of whole-body irradiation followed by infusion of marrow from an HL-A matched sibling. Three patients with advanced leukemia showed histologic evidence suggestive of engraftment but the graft did not function and they died after 18, 26, and 30 days. Four patients, three with acute lymphoblastic leukemia and one with Hodgkin’s disease, treated while in good clinical condition, showed evidence of a functioning marrow graft within 3 wk. Engraftment was proved by cytogenetic analysis in three cases with donors of the opposite sex. One patient died with graft-vs.-host disease (GVH) after 37 days. The other three had mild to moderate GVH. Two patients showed recurrent leukemia and died after 85 and 102 days. In one of these patients, a girl, the recurrent leukemia was in male donor cells. One patient, a boy, is alive and well after 200 days with only female donor cells in the marrow. He shows no evidence of GVH and, as yet, no leukemia.