Forty patients with primary liver carcinoma and 52 with liver secondaries underwent careful preoperative evaluation using computed tomography and magnetic resonance imaging, as well as intraoperative studies using intraoperative ultrasound (IOUS). The results were compared to histological findings. In the 40 patients with primary tumors who underwent hepatic resection, 4 (9.1%) additional lesions were found using IOUS, and in 10 (25%) instances, our preoperative strategy was changed (either a more extensive or more conservative excision was performed). In the 52 cases with metastatic disease who underwent hepatic resection, 14 (21.2%) more lesions were detected, and in 15 (29%) patients, the preoperative strategy was changed. Based on IOUS findings, of 92 patients, a total of 18 (16.4%) additional lesions were detected; in addition, our preoperative strategy changed in 25 (27.2%) of the cases with primary and secondary liver tumors.