Abstract The food frequency questionnaire (FFQ) is the most commonly used dietary assessment instrument for large epidemiological studies because it collects “usual” diet information at a low cost to researchers, and imposes a low burden to survey participants. The FFQ consists of a list of foods with little descriptive detail, and the respondent answers questions about the frequency of each food on the list. A FFQ food composition database links each food in the list to its associated food component values. The steps required to develop a food composition database for a FFQ are to define the purpose of the study, identify the source(s) of data, create a food list, make decisions about the need for portion size information, and incorporate the food component values into the database. The sources of data most often used in the United States are the US Department of Agriculture (USDA) Nutrient Database for Standard Reference or the USDA Food and Nutrient Database for Dietary Studies. Rather than develop a new FFQ for a study or survey, researchers may evaluate current, validated FFQs to determine if they can be used.