Examined in this booklet, one of a series intended to apply economic principles to major social and political issues of the day, are such questions as the origins of interest in combating pollution, why people pollute, continuing interest in the issue, the social costs of pollution, and a possible solution to the problem, all considered from an economic point of view. It is argued that the common thread among all forms of pollution is the existence of spillover costs passed from the polluter to the surrounding area, rather than absorbed as part of the production costs. Thus, factories pollute because the costs of pollution generally fall into areas which are not privately owned, such as the air or rivers. It is emphasized that assessing costs of pollution is often difficult, because the people affected are often already being compensated, by higher wages for more dangerous work or by paying less for housing near the noise of an airport. Graphs are used to demonstrate the marginal costs to society of additional units of pollution, the marginal benefits derived from lower costs for waste disposal, and the intersection of the two. With regard to present pollution control efforts, which focus on rules and subsidies to combat pollution, such efforts are expensive and might better be replaced by alternative methods. For example, a pollution tax matched to spillover costs or a market for pollution rights would permit a certain amount of pollution to be discharged and companies could vie in the marketplace to purchase these rights. (IS)