Questions on voluntary association memberships have been used extensively in social scientific research for decades. Researchers generally assume that these respondent self-reports are accurate, but their measurement has never been assessed. Respondent characteristics are known to influence the accuracy of other self-report variables such as self-reported health, voting, or test scores. In this article, we investigate whether measurement error occurs in self-reports of voluntary association memberships. We use the 2004 General Social Survey (GSS) questions on voluntary associations, which include a novel resource: the actual organization names listed by respondents. We find that this widely used voluntary association classification scheme contains significant amounts of measurement error overall, especially within certain categories. Using a multilevel logistic regression, we predict accuracy of response nested within respondents and interviewers. We find that certain respondent characteristics, including some used in research on voluntary associations, influence respondent accuracy. Inaccurate and/or incorrect measurement will affect the statistics and conclusions drawn from the data on voluntary associations.