The medical use of botulinum toxin as a therapeutic drug began after purification into cristallin form and the subsequent discovery that the injection of small amouns of botulinum toxin into hyperactive muscle caused temporary " muscle relaxation". Nowadays the clinical indication for botulinum toxin are rapidly growing, ranging from treatment of overactive skeletal and smooth muscle to management of hypersecretory and painfull disorders. The various botulinum toxins possess individual potencies, and care is required to assure proper use and avoid medication errors.