Food security is defined as the situation when all people, at all times, have physical and economic access to sufficient safe and nutritious food to meet their dietary needs and food preferences for a healthy and active life (FAO 1996). According to official figures, 24.8% of Mexican population experienced moderate or severe food insecurity in 2010. This represents an increase of 3.1 percentage points with respect to 21.7% in 2008. In other words, this represents an increase of 4.1 million individuals, from 23.9 to 28 million, living under these conditions in two years, from 2008 to 2010 (CONEVAL 2011). CONEVAL validated the Mexican Food Security Scale (EMSA, for its acronym in Spanish) as a reliable instrument to measure food security using Rasch model at the national and state level in Mexico (Carrasco, Peinador, and Aparicio 2010). Despite the validity that the food security scale is proved to have, to the best of our knowledge, there is no available study that has intended to find association between demographic factors and food insecurity at a national level in Mexico. This study will bridge the gap in the literature regarding the identification of factors that determine food insecurity in Mexico. The data used in this study come from The Socioeconomic Conditions Module (MCS 2010, for its acronym in Spanish) of the National Household Income and Expenditure Survey (ENIGH, for its name in Spanish) in the third quarter of 2010. In this study we use an ordered probit model, along with nationally representative data and a newly developed food security scale for Mexico. The analysis was conducted for the general (total) population first and then for a subpopulation group of rural lower-income households. We found that households with younger, less-educated household heads were more likely to suffer food insecurity. Other groups that were found to be vulnerable in terms of food insecurity include: households headed by a single, widow or divorced mother, households with disabled family members, households with strong indigenous background, rural households, low income families, non-agricultural households and households with kids.