Recently, several updates tracking the progress of companies involved in the waste-to-energy field in the United States have been published. World Wastes has compiled this report using several of these resources, including The Resource Recovery Yearbook published by Governmental Advisory Associates Inc. ; the Industry Analysis, published by Kidder, Peabody and Co. Inc. ; Refuse to Energy Markets, published by Frost & Sullivan Inc. ; the Semiannual Survey of Resource Recovery Activities, published by the U. S. Conference of Mayors; and research compiled by Combustion Engineering. The number of waste-to-energy plants in the United States, either in use, under construction or in the planning stages, differs among reports. Some of this variance is due to unclear definitions of terms. Various stages of planning and construction also are defined differently. Construction of resource recovery facilities is similar to other large investment projects. One company may serve as the project manager and is responsible for overall building of the facility. The project manager contracts other services to provide specific equipment or skills. Most project managers have the capability to handle all aspects of plant design and construction and to build plants on a turnkey basis. These full-service suppliers also may assist in financing, equity participation and operation. Refs.