AbstractThe cholinergic nerve fibers, which employ acetylcholine (ACh) as a neurohumoral transmitter, and the results of their activation are listed. The reactions between the enzyme acetylcholinesterase (AChE), its natural substrate, ACh, and the various types of inhibitors are described. The limited therapeutic uses of the anticholinesterase (anti‐ChE) agents are considered. The toxicological effects encountered when the anti‐ChE agents are employed as insecticides or as chemical warfare (CW) agents are discussed. Certain anti‐ChE agents produce also a delayed neurotoxic effect which is apparently unrelated to the inhibition of AChE.