Among the many protein modifications methylation is being investigated actively with regard to bacterial chemotaxis, gene regulation, muscle contraction, cytochrome c methylation, and the synthesis of the acyl transporter, carnitine. In this study the activities of protein methylase I, II, and III in pancreatic tissues of rat, mouse, and guinea pig were examined. Furthermore, the effect of cholinergic agents on the activity of protein methylases in pancreatic fragment of guinea pig was also examined in order to test the relationship between protein methylation and pancreatic secretion. The results are as follows. 1) The activities of protein methylases were generally high in pancreatic tissues of guinea pig and mouse but low in the tissue of rat. 2) The cholinergic stimulants, acetylcholine and carbachol at a concentration of $10^{-5}M$ decreased the activities of protein methylase I, II, and III compared with unstimulated control. 3) The inhibitory effect of the cholinergic stimulant on the activities of protein methylases was not blocked by atropine at a concentration of $10^{-5}M$