Chloroform is a clear colorless, volatile liquid with a pleasant etheric odour. It is mainly used in the production of chlorodifluoromethane (HCFC-22), which is used (in decreasing quantities) as a refrigerant and (increasingly) as a fluoropolymer feedstock. Chloroform may be released into the environment from HCFC-22 plant and from pulp and paper mills using chlorine-based chemicals for bleaching and disinfection purposes. It is estimated that about 90% of total chloroform emissions into the environment are natural in origin. Chloroform is also the principal by-product of water disinfectant processes such as chlorine-chloramine, chlorine-chlorine and ozone-chlorine treatment. Levels vary widely depending upon concentrations of organic materials in the raw water, and are also influenced by treatment method, temperature and pH. This book evaluates the risk to human health and the environment posed by exposures to chloroform. Human data on its toxicity are limited, but the liver is a key target organ in laboratory animals and likely to be so in humans.