Community-based charitable food assistance programs have recently been established in several affluent nations to distribute public and corporate food donations to 'the needy'. In Canada, food banks comprise the primary response to hunger and food insecurity, but problems of unmet food need persist. We conducted an ethnographic study of food bank work in southern Ontario to examine the functioning of these extra-governmental, charitable food assistance programs in relation to problems of unmet need. Our results suggest that the limited, variable and largely uncontrollable supply of food donations shaped the ways in which food assistance was defined and the practices that governed its distribution. Workers framed the food assistance as a supplement or form of acute hunger relief, but generally acknowledged that the food given was insufficient to fully meet the needs of those who sought assistance. In response to supply limitations, workers restricted both the frequency with which individual clients could receive assistance and the amount and selection of food that they received on any one occasion. Food giving was essentially a symbolic gesture, with the distribution of food assistance dissociated from clients' needs and unmet needs rendered invisible. We conclude that, structurally, food banks lack the capacity to respond to the food needs of those who seek assistance. Moreover, the invisibility of unmet need in food banks provides little impetus for either community groups or government to seek solutions to this problem.