Mood disturbance occurs commonly during the postpartum period. The symptoms may be transient and relatively mild (as in postpartum blues) or may be associated with significant impairment of functioning (as in postpartum depression and puerperal psychosis). Despite the prevalence of postpartum mood disorders, depressive symptoms that emerge during the puerperium are often overlooked. Puerperal affective illness places the mother at risk for the development of recurrent depression and has also been associated with significant long-term effects on child development and behavior. Therefore, the prompt recognition and efficacious treatment of puerperal mood disorders are essential in order to avoid adverse outcomes for both mother and infant. This article discusses the evaluation of postpartum mood disturbance and offers guidelines for the treatment of affective illness during the puerperium.