['Up to one fifth of patients with carcinoma of the colon have occult liver metastases at the time of presentation. Intra-operative hepatic ultrasonography might improve disease staging. We report the use of intra-operative ultrasonography (IOUS) in routine clinical practice over a five-year period.', 'Seventy-six patients with colorectal carcinoma (F 21, M 55) of median age 67 years (range 43-89 years) for whom full data were available had IOUS at the time of colonic resection. All patients had had a computerized tomography (CT), magnetic resonance imaging (MRI) or ultrasonography (USS).', 'Of 76 patients, 10 had a Dukes A, 32 had a Dukes B and 34 a Dukes C carcinoma. In 20 patients IOUS detected lesions not seen on pre-operative scanning including 11 metastases (one suitable for resection), seven benign hepatic cysts and two were benign hepatic nodules. Forty-nine patients have remained free of disease and 25 have died with systemic disease (mean survival 10 months, range 2-24 months). In the seven patients diagnosed as having hepatic cysts at IOUS two have died of systemic disease. The remaining patients (n=12) who died with systemic disease had a negative IOUS.'] Does the routine use of intra-operative ultrasound in patients with colorectal cancer improve the detection of hepatic metastases?