Abstract Background The accuracy of laparoscopic ultrasonography in staging pancreatic and periampullary tumours in a referral unit was determined and its use for the subgroup of tumours of stage T3 or greater was assessed. Methods From a larger series of staging laparoscopies 22 patients with pancreatic lesions and five with periampullary tumours who were being considered for resection were staged with laparoscopy and laparoscopic ultrasonography. Only patients with computed tomography (CT) or magnetic resonance imaging (MRI) scans indicating potentially or equivocally resectable disease were included. The laparoscopist was blinded to the results of CT and MRI. Laparoscopy and laparoscopic ultrasonography were undertaken according to a standard protocol using a B & K Medical Diagnostic Ultrasound System 3535 with a colour flow Doppler module. Ascitic fluid was sent for cytology and metastatic disease was biopsied. Results were recorded on a pro forma which included an assessment of resectability. In the case of large tumours this included an assessment of the potential for a positive resection margin or the need for portal vein resection to obtain tumour clearance. The decision to pursue resection was made by the consultant surgeon, based on all the information available including that from laparoscopic ultrasonography. No patient was denied a surgical exploration on the basis of local irresectability determined only by laparoscopic ultrasonography. The predictions regarding resectability were compared with findings at open surgery and with histology. Results Assessment of irresectability by laparoscopic ultrasonography resulted in nine true positives, 16 true negatives, no false positives and one false negative. For pancreatic adenocarcinoma there were eight true positives, 13 true negatives and one false negative. Among the pancreatic group ten of 13 tumours correctly predicted as resectable were stage T3 or greater (Union Internacional Contra la Cancrum, 1997). Of those predicted to be irresectable, all eight were T3 or greater. Among this latter group three were predicted to be irresectable on the basis of local factors alone, two on the basis of metastatic disease alone and three on the basis of both local factors and metastases. Overall, for detection of irresectable disease laparoscopic ultrasonography had a positive predictive value of 100 per cent, a negative predictive value of 94 per cent and an accuracy of 96 per cent. Accuracy was 95 per cent for both the pancreatic tumour subgroup and the T3 pancreatic subgroup. Conclusion Laparoscopic ultrasonography was accurate for predicting irresectability in this group of referred patients. The technique was also accurate for the subgroup with T3 or greater pancreatic tumours.