Depression is a common disorder in women of childbearing age. Many women experience depressive symptoms during the postpartum period, ranging from mild postpartum blues to significant mood disorders such as postpartum depression and postpartum psychosis. The 'baby blues' are extremely common, affecting 30-75% of new mothers. This form of postpartum mood change is self-limited and requires no specific treatment other than education and support. While less common, occurring in 10-15% of births, postpartum depression has the potential for significant impact on both the health of the mother and baby. Unfortunately, affective illness in women frequently goes unrecognized and untreated. While there are effective pharmacological treatments for postpartum depression, the treatments for postpartum depression are often not utilized due to concerns about lactation. Postpartum psychosis is extremely rare, affecting one to two women per 1000 births; each case represents a true psychiatric emergency. Identifying and treating postpartum affective illness in women is critical to the health of both mother and infant. This paper reviews the literature on the diagnosis and treatment of mood disorders in the postpartum period: postpartum blues, postpartum depression and postpartum psychosis.