Multiple definitions of dietary fiber have been developed and are in use around the world. The definitions vary as to which substances are considered to be fibers, the analytical methods utilized to identify and measure these fibers, and whether physiological criteria are part of the definition. A workshop entitled “Dietary Reference Intakes: Implications for Fiber Labeling and Consumption” was held by the International Life Sciences Institute North America Technical Committee on Carbohydrates to review the fiber definitions recently published by the Institute of Medicine (IOM) of the National Academies. Presentations and facilitated discussions reviewed the rationale for the IOM definitions of dietary fiber, functional fiber, and total fiber in light of evolving nutritional science. Also discussed were potential analytical, regulatory, and consumer issues involved if the US Food and Drug Administration and/or Health Canada were to implement the IOM's recommendations. Issues, concerns, and questions to be addressed are summarized here.