In this study we evaluated some pathophysiological aspects of pancreatic and liver ribonucleases and alkaline deoxyribonuclease and their clinical usefulness in diagnosing pancreatic cancer. Pancreatic RNase was found to be a sensitive index of pancreatic malignancy; however it was not specific in distinguishing pancreatic malignancy from chronic pancreatitis or other pathologies. Liver RNase and alkaline DNase did not provide better results than pancreatic RNase. These three enzymes were found to be age-dependent and related to each other. Therefore serum nucleases are not useful for clinical purposes since they are influenced, at least in part, by different non-specific factors.