This document summarizes the pharmacology of the autonomic nervous system. It describes drugs that act on the sympathetic and parasympathetic divisions, including sympathomimetic drugs that cause norepinephrine release or block adrenergic activity, parasympathomimetic drugs, anticholinesterase drugs that potentiate parasympathetic effects, and antimuscarinic drugs that block cholinergic activity. It also discusses drugs that stimulate or block autonomic postganglionic neurons, such as acetylcholine, nicotine, and ganglionic blocking drugs like hexamethonium.