The Los Angeles Family and Neighborhood Survey (L.A.FANS) is a longitudinal study of families in Los Angeles County and of the neighborhoods in which they live. L.A.FANS was originally designed to answer key research and policy questions in three areas: the effects of neighborhoods and families on children's development; the effects of welfare reform at the neighborhood level; and the process of residential mobility and neighborhood change. L.A.FANS also provides a data set for studying other important social, economic, and policy issues, including: adult health and health disparities, immigrant well-being, social ties and neighborhood interaction, marriage patterns, ethnic identity, family survival strategies, family dynamics, health insurance coverage, and self-reported vs. measured health status. The first wave (L.A.FANS-1), which was fielded between April 2000 and January 2002, interviewed adults and children living in 3,085 households in a diverse stratified probability sample of 65 neighborhoods throughout Los Angeles County. In Wave 2 of L.A.FANS, the authors attempted to reinterview in person all primary respondents from Wave 1 who were residing in Los Angeles County, whether or not they continued to live in their Wave 1 neighborhoods. In addition, they interviewed a sample of individuals who moved into each sampled neighborhood between Waves 1 and 2. Fieldwork for the second wave of L.A.FANS took place between August 2006 and December 2008.