Whilst most research on breast-feeding has been designed to assess its importance for infant health or to find a human nutrient replacement for infant formula, the effects of breast-feeding on maternal health have received little scientific attention. In several animal studies lactation has been shown to be associated with a marked blunting of physiological and behavioral responses to physical and psychological stress. However, the literature on the effects of lactation on stress in humans remains limited. This review focuses primarily on recent findings on the effects of breast-feeding on neuroendocrine and behavioral responses to acute stress exposure in lactating women. The available data suggest that breast-feeding suppresses the hypothalamic-pituitary-adrenal (HPA) axis response to physical and psychosocial stress. However, lactation in women, in contrast to lactating rats, does not seem to result in a general restraint of the endocrine stress response during the whole period of lactation. Recent data strongly suggest that the blunted HPA axis response to stress in women seems to be counterbalanced if the acute stressor, at least when of a psychosocial nature, occurs later than 1 h after suckling. Further elucidation of the underlying psychobiological mechanisms involved in suppressed stress responses during lactation will no doubt lead to new insights into improved health sequelae of breast-feeding in women and to a better understanding of the psychobiology of human stress protection in general.