This document outlines agenda-setting theory as developed by Donald Shaw and Marshall McCombs. It provides biographies of Shaw and McCombs, who established agenda-setting theory based on a study of the 1968 US presidential election. The document defines agenda-setting theory as the ability of media to influence public perception about what issues are important. It describes the core assumptions of agenda-setting theory and discusses who sets the media agenda, types of agenda-setting, the effects of media on public agenda, levels of agenda-setting, framing, criticisms of the theory, and conclusions.