Between 1985 and 1987, I presented a series of lectures for the U.S. Environmental Protection Agency (EPA) and the American Chemical Society on physical, chemical, thermal, and emerging technologies for hazardous waste treatment. I always concluded these presentations with a description of a rapidly growing field, the restoration of contaminated soil and groundwater by microorganisms. The promise of low-cost, effective bioremedation at ambient conditions was exciting, not only for the researches developing these novel approaches but also for industry, government, and the public. Subsequently, as I began to apply these techniques to solving waste problems for two of the leading remediation companies in Noth America, it became apparent that potential users of bioremediation considered the technique to be unproven and in the early stages of development. This skepticism existed despite the frequent use of bioremediation at many chemical spill sites and in land treatment of oily wastes in the petroleum industry. Consequently, beginning in 1989, my colleagues and I decided to search for examples of successful field bioremediation that could be documented and used to help commeracilize the technology. It is our hope that this collection of papers and the rapidly growing literature in this field will help turn this developing science into a commercially usable technology.