Intracaval tumour extension represents a significant surgical problem in patients with renal cell carcinoma. Although pre-operative imaging techniques provide sufficient visualization for the planning of the majority of operative procedures, intra-operative ultrasound is nonetheless beneficial in some cases. In 3 patients, the procedure has given an accurate evaluation of the extent of the tumour thrombus. It has allowed safe placement of instruments which had lessened the risk of thrombus dislodgement. Intra-operative sonography is simple to perform and can be considered a valuable new adjunct in the evaluation and management of renal cell carcinoma with intracaval tumour extension. New technological advances may eventually improve the quality of intra-operative imaging.