Telomerase activity was measured in surgically resected tissues in various pancreatic diseases. Relative telomerase activity was expressed as the number of MIA PaCa-2 cells containing an equivalent activity in 1 microgram protein from samples. Telomerase activity in carcinomas was significantly higher than in the other nonmalignant pathologic states. Subsequently, telomerase activity was measured in pancreatic juice from patients with carcinoma, adenoma, and pancreatitis. Telomerase activity in carcinoma samples was significantly higher than that in either pancreatitis or adenoma samples as in tissue samples. High activity of telomerase in pancreatic juice indicates the existence of pancreatic cancer and may serve as a diagnostic tool.