In recent years, both mass communication and personal communication have attracted increased interest as sources of persuasive information which influence individual voting decisions. However, few efforts have so far been made to investigate how mass communication and personal communication interact with regard to electoral decision making. Katz and Lazarsfeld's ‘filter hypothesis’ maintains that personal communication mediates the influence of mass communication on individual voters, reinforcing or blocking the impact of media information, depending on the evaluative implications of that information and on the political composition of voters' discussant networks. This hypothesis is examined and corroborated here, using comparable national election studies from Britain, Spain, the United States and West Germany.