The report gives results of an examination of automatic control theory and its practical applications to environmental processes. A summary is given, emphasizing aspects of the theory that are likely to find application in optimizing environmental control systems. Several case studies, chosen based on the potential applicability of automatic control processes, are used to illustrate applications of several automatic control concepts. The basic equations are introduced in the development of a closed-loop transfer function for a blast furnace scrubber water recycle system. The mathematical complexities of handling a distributed parameter system are illustrated in a study of an acid gas removal system. The possibility of utilizing feed-forward control is illustrated in an examination of fluidized-bed combustion with limestone control. Evaluations of various control options are considered within the context of a limestone scrubber slurry treatment system.