A multitrial design involves an experimental or field investigation that involves multiple treatments or conditions that are provided in a sequence. Most social science investigations, by contrast, consist of a single incident or exposure and then measure the impact of the exposure in a posttest, or a pretest/posttest design. This entry examines how multiple trials can be used in social science research and specifically, communication research. This entry further considers the theoretical assumptions underpinning multiple-trial design and some of the limitations associated with this approach.