The activity of acetylcholinesterase and butyrilcholinesterase was studied during prolonged seizures developing from a primary-cortical focus. The activity was found to spread both along the wide limbic system, which indicates to participation of cholinergic agents in processes of "recurrent generalization" of excitations, and along the horizontal system of fibers connecting both hemispheres. This latter finding indicates to participation of cholinergic mediatory mechanisms in formation of seizures.