Tumor-induced pancreatic damage or insulin resistance may be responsible for diabetes in pancreatic cancer (PC) patients, but the exact cause of association remains controversial. In this study, we aimed to investigate the prevalence of diabetes in patients with PC in central Anatolia, Turkey, and to evaluate whether diabetes is caused by PC. A total of 40 patients with primary PC were enrolled in the study. 13 (32.5%) of the patients had diabetes before PC diagnosis. Oral glucose tolerance test was performed in the remaining 27 patients. The period between the diagnosis of diabetes and detection of PC was less than 1 year in seven (17.5%) patients who had previous diabetes. Recent-onset diabetes and impaired glucose tolerance were detected in 13 (32.5%) and two (5%) of the PC patients, respectively. The prevalence of recent-onset and shortly-before-diagnosed diabetes has been found very high (50%) in our patients with PC. Interestingly, we determined higher levels of insulin and C-peptide in PC patients having abnormal glucose tolerance than patients having normal glucose tolerance. In conclusion, as it has been reported in other population, we determined high prevalence of diabetes in PC patients in central Anatolia. High insulin and C-peptide level indicate that different mechanisms such as insulin resistance may be responsible for abnormal glucose tolerance in PC patients other than the tumor caused insulin deficiency. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.