Three patients with Chediak-Higashi syndrome underwent allogeneic bone marrow transplantation between the ages of 2 years 9 months and 7 years. The outcome was uneventful, with sustained mixed chimerism. No subsequent recurrent infections or hemophagocytic syndrome were observed. At the age of 22 to 24 years, these 3 patients developed a neurologic deficit combining difficulty walking, loss of balance, and tremor. Neurologic evaluation demonstrated cerebellar ataxia and signs of peripheral neuropathy. Moderate axon loss and rarefaction of large myelinated fibers were observed on semithin sections of peripheral nerve. Cerebellar atrophy was detected by cerebral magnetic resonance imaging in 2 patients. We also reviewed the very long-term outcome of the other 11 patients with Chediak-Higashi syndrome who had received bone marrow transplants at our center since 1981. All displayed neurologic deficits or low cognitive abilities.