Intraoperative sonography (IOS) of the pancreas was performed in 12 patients, eight with known or suspected inflammatory disease and four with known or suspected malignancy, in order to assess its utility in aiding pancreatic surgery. In all eight patients with inflammatory disease, IOS provided additional information, aided in resection or biopsy, or identified structures that could not be evaluated by surgical dissection. IOS was particularly useful in these patients in determining the size and appearance of the pancreatic duct before dissection or ductography, thus allowing planning of appropriate pancreatic decompression or resection. It also was extremely helpful in locating and characterizing pseudocysts, including measurement of cyst wall thickness, and in directing needle aspiration of cyst contents. Adequate drainage of all cysts in multiple cystic masses was easily monitored. Finally, impalpable peripancreatic fluid collections and abscesses were often localized. In the four patients with probable malignancy, IOS was somewhat helpful in two, allowing exclusion of tumor in one and guiding biopsy in another. In the other two patients, IOS provided no information due to obvious local invasion and nonresectability. Results indicate a significant adjunctive role for IOS in surgery for inflammatory disease of the pancreas. It seems to be less helpful in patients with malignancy, probably because of the advanced stage of pancreatic carcinoma at the time of surgery.