A 155-year-old woman was admitted to hospital in June 1995 with a history of chronic pain in the left hip of several months duration. Clinical examination revealed tenderness in the left hip and pelvis but no lymphadenopathy or hepatosplenomegaly. Radiography of the left pelvis and hip showed severe destruction of left iliac bone and acetabulum (left panel). Skeletal survey showed no evidence of other bony abnormalities. A CT scan of the abdomen and pelvis demonstrated a large soft tissue tumour arising in the left iliac wing destroying most of the iliac bone and extending into the left sacral ala (right panel). A CT-guided biopsy of the tumour confirmed a diagnosis of lymphoplasmacytic lymphoma. Bone marrow biopsy showed no unequivocal evidence of lymphomatous infiltration. The patient was treated with combination chemotherapy containing cyclophosphamide, vincristine, doxorubicin and prednisolone (CHOP) followed by local radiotherapy. The patient responded to the treatment well and was gradually mobilized. The most recent radiography and CT scan show that her disease is under control and some degree of bone re-ossification has taken place. Clinically she is well, pain free and able to walk.