The principal role of acetylcholinesterase (AChE) is believed to be termination of impulse transmission by hydrolysis of the neurotransmitter acetylcholine, and development of cholinergic synapses is indeed accompanied by accumulation of this enzyme. The biosynthesis of AChE is of interest for a number of reasons: it is a synaptic enzyme whose regulation and assembly may involve both pre- and postsynaptic control, and it exists in multiple molecular forms differing in their localization, mode of association with the surface membrane, regulation and, presumably, physiological functions. Moreover, it may be expected that certain of these molecular forms may undergo novel modes of post-translational processing and modification in the course of their integration into the functional synapse. A number of groups have studied the appearance and regulation of AChE in cultures of nerve and muscle. This chapter demonstrates that Xenopus oocytes synthesize and secrete catalytically active AChE upon microinjection with poly(A)-containing RNA prepared from whole rat brain, from dissected rat cerebellum and from Torpedo electric organ. The chapter further defines the stability and efficacy of the injected AChE-mRNA and, on the basis of the amounts of mRNA injected and AChE secreted, present calculations demonstrating that AChE-mRNA is a scarce mRNA species in both rat brain and Torpedo electric organ.