Opinion polling is a method of analysis for drawing inferences about the attitudes or behaviors of a population by studying a random sample of persons from that population. Nonrandom surveys are sometimes used by social scientists for theory building, but only random samples can produce valid estimates of population traits. Since social scientists are typically interested in population traits, and since few other methods are as useful for studying population traits at the level of individuals, opinion polling with random samples has become one of the most common methods of data collection in the social sciences. Space does not allow a full treatment of this topic internationally and across the social sciences, but detailing the early adoption and continued use of opinion polls for political science research in the United States provides a useful introduction to the reasons why opinion polling remains such an important tool for the social sciences.