Systemic chemotherapy is a well known cause of reversible hair loss. Busulfan chemotherapy, however, is responsible for a permanent alopecia that usually occurs in bone marrow transplant patients. We report two patients with permanent alopecia due to busulfan chemotherapy. Both patients had a diffuse alopecia characterized by greatly reduced hair density with short, thin hair. The pathology showed reduced follicular density in the absence of fibrosis, suggesting that alopecia may result either from hair follicle stem cell destruction or from acute damage to the keratinocytes of the lower portion of some follicles.