A 5-year-old Chinese boy had dull pain in his right knee for about one year. An intraosseous osteolytic lesion in the metaphysis of the right lower femur was curetted. The diagnosis of desmoplastic fibroma, possibly the first in a Hong Kong Chinese, was based on the clinical, radiological and histological findings. About one year later the only abnormality was a small rounded radiological lucency, static for 4 months. The fibroblastic nature of the lesion and its tendency to local recurrence support a fibromatosis of intraosseous origin.