Botulinum neurotoxins are the most potent natural toxins known, produced by the anaerobic spore-former botulinum and certain strains of other clostridia. The neurotoxins cleave synaptic proteins and block acetylcholine release in cholinergic nerves, causing a flaccid paralysis. While large doses of toxin, ingested with food or feed or synthesized by the bacteria in the gut or deep wounds of humans and animals, cause a life-threatening paralysis, botulism, controlled administration of minute amounts of the neurotoxin is becoming the first choice in treating an increasing number of spastic and many other disorders. Considering the severity of botulism but also the wide range of therapeutic applications, knowing the regulatory mechanisms behind botulinum neurotoxin synthesis is of utmost importance. Nevertheless, only little is known about this control. The talk will focus on the pathogenesis of botulinum neurotoxins and their therapeutic use, and gene regulation in C. botulinum.