This study develops a framework for differentiating true Food Stamp Program (FSP) impacts on food security from those that arise because households with the most severe food-related hardships are more likely to participate in the program. The framework hypothesizes that food spending improvements are the likely causal link between FSP participation and enhanced food security. Since food stamp benefits diminish with income, the incremental effect of FSP participation is also expected to diminish. Using data from the Current Population Survey Food Security Supplements in a statistical framework that controls for household income, the study finds that FSP participants have consistently higher at-home food spending and lower away-from-home-spending than comparable nonparticipants. For both groups, food security rises with income, but food security remains lower for program participants. Because differences in food spending and food security do not disappear as income rises, the study concludes that observed disparities are not likely to be true program impacts.