With the present increased incidence of breast-feeding, clinicians need to be prepared to identify and manage problems in lactation. Most problems are related to insufficient knowledge, inappropriate routines, and lack of confidence and are easily managed or prevented by prenatal education, anticipatory guidance, and adequate support. Increasing evidence exists that primary causes of lactation failure also occur and can preclude successful lactation, even among highly motivated women. Three cases are presented in which lactation failure is believed to stem from insufficient glandular tissue within the breasts. Supportive history for this entity include absence of typical breast changes with pregnancy and failure of postpartum breast engorgement to occur. Associated physical findings included a unilateral underdeveloped breast in each woman and palpable patchy areas of glandular tissue in one case. Breast diaphanography, or transillumination, substantiated clinical findings in the two cases in which it was performed. Both multiparous women had a previous unsuccessful breast-feeding experience, whereas the primiparous woman had immediate family members with a history of lactation failure. All three women benefited psychologically from the interpretation that lactation failure was not due to their breast-feeding performance, and each elected to continue nursing long-term despite the need for formula supplement. These cases are presented to emphasize that primary causes of lactation failure do exist and to alert clinicians to the historical and physical findings suggestive of inadequate glandular tissue as an etiology of previously unexplained lactation failure. Preserving the "every woman can nurse" myth contributes to perpetuating a simplistic view of lactation and does a disservice to the small percentage of women with primary causes of unsuccessful lactation.