This chapter contains sections titled: Introduction Role of Acetylcholinesterase and Mechanism of Cholinergic Neurotransmission Effects of Organophosphates and Carbamates on Acetylcholinesterase Effects on Release, Synthesis, and Storage of Acetylcholine Effects on Acetylcholine Receptors Effects on Neuroactivities Other than the Cholinergic System Conclusions Acknowledgments References