A 34-year-old man with a subtrochanteric osteoid osteoma localized to the lateral cortex of the left femur is reported.The patient presented with mild spontaneous pain of the lateral thigh and knee.He refused a radiographic examination and was treated as a greater trochanteric pain syndrome for 9 months.He was then admitted with a transcervicai fracture of the neck of the left femur after a fall from standing height.The fracture was fixed with 3 cannulated screws and healed uneventfully.His symptoms worsened after the first postoperative year.Eighteen months postoperatively the pain was dull,worsening at night,and relieved only with anti-inflammatory drugs,and he had a limp.New radiographs and tomograms were indicative of a lateral subtrochanteric osteoid osteoma with a subperiosteal localization.The lesion was treated successfully with surgical excision of a piece of reactive bone including the nidus.