An HLA-identical sibling bone marrow transplant was done for a patient with Chediak-Higashi syndrome. The preparative regimen included intravenous fludarabine (40 mg/m2/dx4) and busulfan (130 mg/m2/dx4). Busulfan was given once daily. Pharmacokinetic studies showed the area under the concentration-time curve of the once-daily intravenous busulfan was similar to that seen with the total daily dose administered with an every-6-hourly regimen. Toxicity was minimal. Myeloid engraftment occurred on day +17 and donor chimerism was complete. Fludarabine and once-daily intravenous busulfan is well tolerated and is adequate for engraftment of sibling transplant in Chediak-Higashi syndrome.