In the public eye, bacteria of the genus Clostridium are often misconceived as being a biological threat and thus a foe to mankind. However, only a few of the more than 150 validly described clostridial species produce potent natural toxins, such as botulinum or tetanus. Furthermore, even these have since become valuable tools in the treatment of severe diseases. Clostridia belong to the avant-garde of biotechnologically important microbes. In the past, they were used for the production of industrial solvents, indigo dyeing, and flax retting. Nowadays, they exhibit enormous potential as producers of industrially important enzymes and in biotechnological processes such as the cleaning-up of dumping sites or raw oil recovery. Therapeutic applications are, for example, the treatment of muscle spasms and cancer therapy. This book will correct the misconception of generally ''bad'' clostridia by providing a comprehensive and up-to-date overview, while also detailing applications of these bacteria, whether already in use or soon to be introduced in the fields of biotechnology and medicine.