While we endorse recent calls for greater collaboration between mass communication and interpersonal communication researchers, in this response we delineate four factors that account for the relative lack of integration of these two areas of communication inquiry. The social policy focus of mass communication research, the high level of public concern over media effects, a variety of methodological cleavages, and different cognate field referents are cited as forces that support segregation of the two research areas. The recent turn to cognitive explanations of communication in both of these domains may create the climate necessary for meaningful collaboration between researchers.