The authors report a rare complication of neurofibromatosis, recurrent rapidly expanding massive subperiosteal hematomas, in the thigh of a 22-year-old woman. The diagnosis was confirmed by plain radiography, ultrasonography and computed tomography. The first two hematomas were drained through a longitudinal lateral incision, tightly closing the periosteum over drains and applying a compression dressing postoperatively. The third hematoma was treated expectantly. Recurrent subperiosteal hematomas may lead to the formation of huge bone cysts and grotesque limb deformity, for which amputation may be the only solution.