Botulinum toxin is a biological toxin elaborated by an anaerobic bacteria clostridium botulinum. It has muscle paralyzing action. Its use in clinical situation was started by Dr. Allan Scott, an ophthalmologist in cases with strabismus about two decades ago Since the onset of its journey it has used in dysfunctions in almost every system of the body where there is muscle hyperactivity. Recently it has been also been used in sensory disorders because of its anti-nociceptive action. This chapter will help the reader to understand the nature of this toxin, mechanism of action and various indications and its application.