Neurotransmission is essential to physiological processes of cellular communication. The search for new molecules that may influence neurotransmission systems is an open field with possible impact on several pathophysiological conditions or diseases: Alzheimer's disease, Parkinsonism and myasthenia gravis, etc. The present review describes the most important aspects of cholinergic neurotransmission, as well as natural and synthetic compounds that, as clinical or experimental drugs, are able to influence this transmission. The pharmacological effects of substances that bind to muscarinic or nicotinic cholinergic receptors, along with their corresponding affinities will also be presented.