Liposarcoma of the renal capsule is a very rare mesenchymal tumour. Since the tumour presents with signs of a solid renal mass, correct preoperative diagnosis is usually difficult. Urography, ultrasound and CT do not always make it possible to distinguish a parenchymal from a capsular mass. The most useful investigation seems to be renal arteriography. In this report a case of capsular liposarcoma is presented. The difficulties of preoperative diagnosis are discussed.