Vihiga, one of the poorest and densely populated districts in Kenya is perpetually food deficit (GOK, 2005). While food demand continued to rise, production fell behind both targeted production and district demand. To make matters worse food deficit situation worsened over the last decade. Rising population and competition for resources have curtailed efforts to improve household food production in the district. Unfavorable poverty indicators in the district only make matters worse. About 57.6 percent of the population and more than 50 percent of households live below absolute poverty line while 57 percent of the population and households live below food poverty line (GOK, 2005). Poor welfare indicators for Vihiga district underscore the importance and urgency for addressing its basic needs. Understanding determinants of food security in Vihiga district will improve targeting, the focus and success of policies for addressing food insecurity. The paper examines food security in a subsistence economy with an application of a Translog cost function to household survey data in Vihiga district to determine the supply side constraints. Cluster sampling was used with divisions forming the main clusters in the district. Using systematic random sampling, 50 households were selected from each cluster resulting in a sample of 300. Results show that scale of production, number of adults, household head, business income, employment; human resource development, capital, and land size significantly influence household food security. Food security programmes, in subsistence economies, aimed at revamping production should focus more on enhancing accessibility to production resources and improving the quality of labor through training. Key Words: Food security, Translog cost function, Vihiga, Kenya