The overarching objective was to allow for broad participation in the biomedical assessments. Thus, all living Project 1 (national survey) respondents were considered eligible for participation if their existing health information indicated an ability to travel to the clinic without excessive risk to the respondent or project staff. Siblings of main sample respondents were not part of the recruitment pool (primarily because of cost), but members of the twin sample were included. Members of the Milwaukee sample of African Americans, newly recruited at MIDUS II, were also part of the recruitment pool. Eligible respondents were first sent a letter explaining what the biological project was about. A brochure sent with the letter sketched the key objectives of the biomedical assessments, outlined what would be included in the clinic visit, and explained how financial matters related to respondents’ time and travel would be handled. Follow-up phone calls were then made to provide additional details and answer any questions the respondent might have. All travel expenses to and from the clinics were covered, and project staff also helped arrange travel itineraries. For aged individuals, or those concerned about traveling alone, an option was provided to travel to the clinic with a companion. Respondents were given $200 in consideration of their two-day visit to the medical clinic. For some, childcare costs were also provided. The study was approved by the Institutional Review Board at each participating center, and informed written consent was obtained for all participants.