Chediak-Higashi syndrome is a rare condition characterized by susceptibility to bacterial infections, defective natural killer activity, and episodes of macrophage activation known as accelerated phases. Chemotherapy can induce transient remission of the accelerated phase, but relapses become less and less sensitive to treatment and ultimately lead to death. Allogenic bone marrow transplantation (BMT) has been proposed as a curative treatment for Chediak-Higashi syndrome. We report the outcome of BMT in 10 such children. Seven received marrow from an HLA-identical related donor and three from an HLA-nonidentical related donor. Three patients died, two from a new accelerated phase after rejection of transplanted bone marrow and one from cytomegalovirus (CMV) pneumonia. Six of seven recipients of HLA-identical marrow and one of three recipients of HLA-nonidentical marrow are alive and well without treatment 1.5 to 13 years after transplantation (median, 6.5 years). No manifestations of accelerated phases have occurred in these seven patients, and significant natural killer activity is detectable. Interestingly, BMT prevented recurrence of accelerated phases in patients with limited numbers of donor-type leukocytes after transplantation. Ocular and cutaneous albinism were not corrected after transplantation. None of the patients developed serious toxic reactions to the BMT conditioning regimen or have long-term sequelae. These results show that HLA-identical BMT is an acceptable curative treatment for Chediak-Higashi syndrome, whereas HLA-nonidentical BMT remains an experimental approach.