Seventy-nine consecutive patients underwent elective laparotomy for symptomatic hepatocellular carcinoma between 1986 and 1992. In the first 4 years, 51 patients received liver resection without intraoperative ultrasonography. In the subsequent 2 years, ultrasonography was performed during operation on 28 patients; three were found to have inoperable tumours. The technique located tumours in two patients and changed the extent of liver resection in another two. Eight of 51 patients (16 per cent) who had the parenchymal transection plane determined clinically had histological evidence of tumour infiltration of the resection margins, compared with none of 25 in whom the plane was determined by ultrasonography. This difference was significant (P = 0.034). The use of intraoperative ultrasonography improved patient survival, although this was not statistically significant. The median survival of patients with adequate resection margins was 9.2 months, compared with 3.9 months in those with inadequate margins. Intraoperative ultrasonography is useful in surgery for hepatocellular carcinoma.