The UW Twin Registry Health Survey was sent from 2006-2008 to members of the Registry who had enrolled by 2006. It was mailed to about 2,300 twin pairs. The Health Survey was used as a follow-up to the Enrollment Survey and included many of the same questions. It also included new questions about general health, eating behaviors, sleep habits, specific health conditions, lifestyle habits, and emotions. Respondents were entered into a raffle after they submitted the survey.