On 28 April 1988, the Interagency Group for Action on Breastfeeding met to develop and agree upon a set of definitions that could be used as standardized terminology for the collection and description of cross-sectional information on breastfeeding behavior. The schema and potential framework suggested at the meeting were reviewed extensively by breastfeeding researchers and program personnel, revised at subsequent meetings by a variety of organizations, and compared against published research on patterns of breastfeeding and their effects on infant nutrition, health, and fertility. This schema and framework: (1) acknowledge that the term "breastfeeding" alone is insufficient to describe the numerous types of breastfeeding behavior, (2) distinguish full from partial breastfeeding, (3) subdivide full breastfeeding into categories of exclusive and almost exclusive breastfeeding, (4) differentiate among levels of partial breastfeeding, and (5) recognize that there can be token breastfeeding with little to no nutritional impact. The schema and framework should assist researchers and agencies in their efforts to accurately describe and interpret breastfeeding practices.