Sixty-seven patients were prospectively studied using grey scale ultrasound (GSU) to assess its possible role as part of a jaundice investigation programme. All scans were performed by one radiologist, without clinical information. When intrahepatic ductal dilatation was found an attempt was made to establish the level and cause of obstruction. The calibre of the intrahepatic bile ducts was correctly reported in 66 patients (98 per cent). Forty-three proved to have extrahepatic cholestasis, 24 had intrahepatic cholestasis. No patient with intrahepatic cholestasis had dilated ducts seen on ultrasound. In 43 patients with obstructive jaundice, GSU accurately detected the level of obstruction in 28. This accuracy varied with the cause of obstruction. A direct indication of diagnosis was possible in 45 of the 67 patients. In a unit specializing in the management of complicated hepatobiliary problems, GSU has been shown to be accurate in differentiating extra- from intrahepatic jaundice. Being non-invasive, it appears ideally suited for use as a screening procedure, permitting selection of appropriate invasive investigations to provide complete preoperative imaging of the biliary tree. In patients with jaundice due to gallstones, GSU may be the only imaging technique required before surgery provided good operative cholangiography is available.