This study investigated the impact of telephone answering machines on telephone survey participation. The study found that households with answering machines were more likely to be contacted, more likely to complete the interview, and less likely to refuse to participate in the study compared to households where there was no answer on the initial call attempt. The study also investigated the utility of leaving messages on the answering machine as a means of encouraging participation. While leaving messages did result in higher participation rates, there were no significant differences among the types of messages tested.