The efficiency of ultrasound in the diagnosis of pancreatic disease was compared prospectively with that of selenomethionine isotope scanning in 46 patients presenting with abdominal pain or weight-loss or with jaundice. Of 14 patients who later proved to have pancreatic carcinoma, all had an abnormal isotope scan and 13 had an abnormal ultrasound scan. Of 10 patients with chronic pancreatitis, all had an abnormal isotope scan and 9 had an abnormal ultrasound scan. The small advantage of selenomethionine was, however, offset by a higher false-positive rate: of 22 patients who proved not to have pancreatic disease, 13 had abnormal isotope scans compared with only 3 with ultrasound. Review of earlier experience with the two techniques yielded similar results: in pancreatic carcinoma and chronic pancreatitis, isotope scanning gave slightly fewer false-negative results than ultrasound but many more false-positives. Because of its lower false-positive rate, because it avoids ionising radiation, and because it can usually distinguish carcinoma from pancreatitis, ultrasound is the procedure of choice for initial investigation of patients with suspected pancreatic disease.