It is known that cAMP and cGMP, as an ''intracellular second messenger system'' play a significant role as a signal system, in the mechanism of action of anti-ulcerogenic (cytoprotective) drugs. According to our present, preliminary investigations it seems that during different experimental circumstances the gastric mucosal 3'-5'-cyclic-cytidine-mono-phosphate (cCMP) 3'-5'-cyclic-uridine-monophosphate and (cUMP) levels were changed-similarly to CAMP and cGMP-and these changes might be a possible indicator of a further, most probably secondary, signal- system role.