Botulinum toxins, exotoxins of Clostridium botulinum, are the most toxic 
naturally occurring substances known to man. For more than a century they are 
known to be the cause of botulism, a nowadays rare intoxication with spoiled 
food that leads to generalized flaccid weakness of striated muscle including 
pharyngeal and respiratory musculature. The toxins act primarily at peripheral 
cholinergic motor nerve endings by blocking the release of the neurotransmitter 
acetylcholine. As a consequence, action potentials in the motor nerve can no 
longer be transmitted to the muscle. This lack in transmission, clinically 
appearing as weakness, may disable or actually critically endanger affected 
patients. However, in certain neurological diseases characterized by an abnormal 
increase in muscle tone or activity, for example dystonia or spasticity, a 
reduction in signal transmission may actually be beneficial. Around 1980 local 
injections of minute amounts (in the order of 0.5 ng) of Botulinum toxin type A 
were first successfully used in a neurological disorder named blepharospasm 
which is characterized by an involuntary squinting of the eyes. Since then 
Botulinum toxin has developed rapidly from a frightful poison to a safe 
therapeutic agent with a remarkable beneficial impact on the quality of life of 
many thousands of patients worldwide. This review tries to outline in brief the 
characteristics of Botulinum toxins, their mechanism of action and the various 
indications for clinical use as a therapeutic agent.