To analyze the effect of IOUS on surgical decision making, we performed a retrospective study of 45 patients who had exploratory laparotomy and IOUS for liver neoplasms. Preoperative lesion detection was compared with intraoperative findings. The effect of IOUS on the choice of surgical procedure was analyzed. Preoperative imaging detected 67% of lesions, 78% when combined with surgical inspection and palpation, and 97% were recognized by IOUS. Surgery was modified in 23 of 45 cases (51%); 19 of those 23 cases (83%) were based on IOUS findings alone. IOUS demonstrated superior lesion detection over noninvasive preoperative liver imaging, and IOUS significantly affected surgical decision making.