The first wave of the NESARC was fielded between 2001 and 2002 and included 43,093 participants who were aged 18 years and older. Of these, a total of 39,959 participants were eligible for wave 2 interviews. Ineligible respondents were those who could not be interviewed because at the time of the follow-up interview they were either deceased, deported, mentally or physically impaired or on active military duty. Of the eligible wave 1 participants, 34,653 were successfully followed and re-interviewed in the wave 2 survey between 2004 and 2005. The response rates for wave 1 and eligible wave 2 surveys were 81% and 87%, respectively.
