This study aimed to analyze the association between food insecurity and certain socioeconomic and demographic variables that measure social inequality: income, schooling, race, family structure, household characteristics, and sewage conditions. A sample of 456 families in Campinas, São Paulo State, was interviewed using the Brazilian Food Insecurity Scale (EBIA). Family food insecurity was associated with: more children < 18 years; precarious housing; overcrowding; lack of sewage system; low income (< 2 times the minimum wage); head-of-household with no schooling; no university graduate in the family; and race (black). Directly measuring food insecurity is important for monitoring inequality, and can be used either with other socioeconomic and demographic indicators or alone to identify social vulnerability in population groups.