The aim of this study was to compare the accuracy of intra-operative ultrasound (IOUS) with other imaging modalities and with surgical palpation in detecting liver metastases from colorectal cancer (CRC). Intra-operative ultrasound was performed in 100 patients undergoing surgery for CRC. All patients had pre-operative liver function tests, transcutaneous ultrasound and computerized tomography (CT) scan of the liver. The liver was palpated intra-operatively by a surgeon who was unaware of the pre-operative findings. The liver was then assessed by IOUS. Intra-operative ultrasound detected more patients with metastases than either CT scan, transcutaneous ultrasound or surgical palpation. It also detected a greater number of smaller metastases in these patients and allowed better anatomical definition compared with pre-operative investigations.