Reducing the possibility of accidental toxic chemical releases reduces the possibility of harm to human health and to the environment. When such a release does occur, however, its consequences must be reduced. This can be accomplished by means of a variety of mitigation measures that can contain, capture, destroy, divert, or disperse the released chemical. Mitigation measures begin with the initial siting and layout of a facility to decrease the area that would be affected by a release. The extent of the area potentially affected, the concentrations of toxic chemicals reaching those areas, and the duration of exposure can be estimated by vapor or gas dispersion modeling. The extent and magnitude of an actual release can be determined using meteorological instruments. These systems, along with emergency planning and training, are the first steps in the mitigation process. Other measures involve the use of mitigation techniques such as leak plugging, containment systems, and spray or foam systems. The general application costs of these methods are discussed.