Organizations measure household food insecurity for program design, planning, targeting, implementation, monitoring, and evaluation, but existing measures often are inadequate. Qualitative and quantitative methods were used to develop and validate an experienced-based measure of the access component of food insecurity in northern Burkina Faso. In-depth interviews on food insecurity were done with 10 household heads and 26 women using interview guides. We identified themes, classified households, created a table of food insecurity categories, identified items to add to or delete from an initial questionnaire, and developed and revised answer choices. A longitudinal study provided quantitative data on changes over time in household food insecurity, economic situation, and related factors. Data were collected on 126 simple and complex households from 9 villages each July and January from 2001 to 2003 (5 waves). These data allowed examination of changes in household food insecurity twice annually across the best and worst seasons for food, and evaluation of the ability of the experience-based measure to differentiate changes in household food insecurity. Validity was assessed by examining reliability and by comparing the experienced-based food insecurity measure with economic status, dietary, and anthropometric measures and with a measure created by an observer who rated the households' food insecurity. The results provide strong evidence that the food insecurity score, calculated from experience-based questionnaire items, was valid for determining seasonal differences in household food insecurity, differences among households in food insecurity at a given time, and changes in household food insecurity over time in northern rural Burkina Faso.