Botulism the disease, the related organism (Clostridium botulinum) and toxin have gained renewed attention in these times of heightened homeland security and bioterrorism preparedness. Since C. botulinum is ubiquitous in nature, botulism outbreaks resulting from environmental exposure can be of concern to watershed managers and drinking water utilities. This paper reviews aspects of naturally occurring C. botulinum in light of concerns for source water watersheds. Information regarding sources and occurrence of botulism, C. botulinum and botulism toxins are discussed. Ecology and physiology of environmental C. botulinum and cycles of disease are reviewed. Finally, the effectiveness of water treatment and disinfection measures is discussed.