Between August 1985 and October 1987 we treated 35 patients with chronic myeloid leukaemia (CML) by high dose chemotherapy, total body irradiation (TBI) (1000 or 1200 cGy, n = 31) and total lymphoid irradiation (TLI) (800 or 600 cGy, n = 35) preceding allogeneic bone marrow transplantation (BMT). Both TBI and TLI were given at 200 cGy/fraction. Twenty-three patients had HLA-identical sibling donors, nine patients had HLA-matched but unrelated donors, and three partially HLA-mismatched donors. Twenty-two patients received T-cell depleted marrow. The addition of TLI to the standard protocol did not add greatly to the toxicity. Four patients had recurrent leukaemia before engraftment was evaluable. The other 31 patients engrafted and no graft failed. Twenty-two patients survive at a median time from transplant of 305 days (range 81-586 days). Fourteen have no evidence of disease; eight have or had only cytogenetic evidence of leukaemia. We conclude that the addition of TLI to pretransplant immunosuppression increases the probability of reliable engraftment in patients receiving T-cell depleted marrow. This benefit is not associated with significantly increased toxicity.