Botulinum toxin is the most potent toxin known. It is readily absorbed from mucosal surfaces. If dispersed as an aerosol or mixed in the food or water it can lead to a large outbreak of botulism. The disease presents as a symmetric descending paralysis in an afebrile patient. Cranial nerve involvement with diplopia, dysarthria, dysphonia, dysphagia and respiratory paralysis is seen after a variable incubation period. The treatment is mainly supportive. The source of the toxin is Clostridium botulinum, an anaerobic gram-positive spore-forming organism. Some other species of Clostridium like C. butyricum and C. baratii also produce the toxin. The toxin is heat labile and can be inactivated by heating at 100°C for 10 minutes. The toxin acts at the peripheral cholinergic nerve terminals at the neuromuscular junctions, postganglionic parasympathetic ganglia, etc, and affects neurotransmitter release by inhibiting exocytosis. Clinical uses in various medical fields were found for it.(AU)