There are a large number of women who perceive a reduction in milk supply. With appropriate, knowledgeable advice, most are able to continue breastfeeding successfully. If an infant is not gaining weight normally, the mother's milk production must be assumed to be low (usually a secondary phenomenon); meanwhile, consider the possibility of an organic problem in mother or infant. The complex interactional nature of the problem requires attention to history, physical examination, differential diagnosis, and thoughtful problem solving. There are situations that require infant supplementation for optimal growth; when this is the case, supplementation should be provided in a way that best supports continued breastfeeding to the fullest extent possible. Anticipatory guidance, early detection of problems, and prompt intervention are the keys to ensuring copious milk production and normal infant growth.