Postpartum Depression (PPD) is an important social and health problem for women and their families with an incidence of at least 13%. In comparing the diagnosis, timing, and symptom patterns of PPD and Major Depressive Disorder (MDD), there are distinct differences that may partially explain why PPD is under-diagnosed and under-treated. The purpose of this manuscript is to compare and critique the most common instruments used to assess PPD. The Postpartum Depression Screening Scale developed by C.T. Beck and Gable is recommended for use by mental health providers.