The ability of animals to respond to pollutants in their environment is a well-known phenomenon. Recently, a program was initiated by the U.S. Environmental Protection Agency to explore the application of monitoring by animals to expedite sampling programs at hazardous spills or waste sites. This paper describes a feasibility study in which a dog/handler team was used to locate low concentrations of a hazardous substance (i.e., trichlorophenol and toluene) hidden in a field, thus suggesting that a dog can be trained to locate such materials on industrial sites, abandoned landfills, etc. The use of a dog/handler team to uncover simulated hazardous wastes infiltrating into buildings such as might be encountered with groundwater leakage, seepage from storage tanks, etc. will also be described. Lastly, the use of dogs to assist workers at a hazardous site in delineating the contaminated area will be discussed. To a limited extent, the use of state-of-the-art portable gas/vapor detection instruments at waste sites will be compared with the application of this new 'instrument'. The experience with and the inherent detection potential of canines will be reviewed and new directions explored.