A 14-year-old boy presenting with primary myelofibrosis (MMM) was treated with alpha-interferon (IFN). After 6 months his spleen was no longer palpable and blood counts had returned to normal. A reversal of bone marrow fibrosis was histologically documented. Although improvement in symptoms and blood counts has been reported, this is only the second description of reversal of bone marrow fibrosis in MMM after treatment.831211241125