An 11-year-old boy developed florid reactive periostitis several years after minor trauma. The symptoms responded initially to antibiotics, but after cessation, rapidly recurred and progressed, requiring a ray amputation to relieve the pain and to achieve a functional hand. The reactive periostitis affected the volar aspect of two adjacent phalanges with sparing of the intervening joint, confirming that this is a reactive process rather than a benign neoplasm.