As the largest of the 15 food and nutrition assistance programs administered by the U.S. Department of Agriculture (USDA), the Supplemental Nutrition Assistance Program (SNAP) is a central component of our nation's nutrition assistance safety net. SNAP provides nutrition assistance benefits and nutrition education services to low-income individuals and families in an effort to reduce hunger and improve the health and well-being of low-income people nationwide. While evaluation research has assessed whether the program is achieving these objectives, less is known about the challenges low-income families face and their coping strategies to remain food secure, defined as having adequate access to food for an active, healthy life. This report presents findings from the qualitative In-Depth Interview component of the SNAP Food Security (SNAPFS) study. The main SNAPFS study was conducted for the Food and Nutrition Service of the USDA from October 2011 through September 2012, and examined the effects of the program on food security for 6,436 SNAP households just entering the program and 3,275 households on SNAP for approximately six to seven months. The in-depth interview effort discussed in this report was conducted between February 2012 and June 2012 and consisted of detailed qualitative discussions held with a small subset of 90 SNAP households with children in six states about their financial situations, their use of SNAP, and their overall food security. Interviews were held in the homes of the respondents, unless they preferred to meet in a public location like a library or coffee shop. Interview questions focused on expenditures and income, SNAP and food shopping habits, eating habits, nutrition, triggers of food hardship, and food-related coping strategies. The purpose of this formative, qualitative study was to provide important insights into the challenges low-income families face and their coping strategies to purchase all of the food that they need in the face of a shortfall in resources, and to inform the direction of future research on food security, including hypothesis generation and instrument design. This analysis was descriptive; however, for each theme, we systematically assessed whether there were especially large differences in general financial circumstances, food hardships and coping strategies, eating and food dynamics, and in the role SNAP plays in meeting a family's nutritional needs by food security level and by race/ethnicity. We observed several of the former but almost no meaningful differences among the latter. As qualitative works which involve similar types of analysis have noted, a small qualitative study cannot make causal claims; therefore, the analysis in this study should be read as helpful descriptions to guide the formation of hypotheses about the mechanisms and processes that might underlie variations in food security, and the role of the SNAP program.