The postnatal period is characterized by an increased risk of psychiatric disorders, which can have severe and disabling effects on the mother and lead to potentially long-lasting developmental or cognitive deficits in the child. Recent studies have indicated that endocrine functioning influences postpartum disorders. Thyroid dysfunction and the level of corticotropin-releasing hormone have both been related to postpartum depression. It is the purpose of this project to determine the relationship between the measures of six hormones and observed mother-infant behavior in baboons to better understand the physiology of postpartum depression in humans. Baboons were chosen for this project because they are common laboratory animals, have been used extensively in reproductive research, have similar reproductive functioning to humans, and allow a standardized, controlled social and physical environment which eliminates extraneous variability inherent in human studies. In addition, the presence of a pedigreed baboon colony will allow future analysis of the influence of genetic variation on promising behavioral or hormonal indicators. Ten female baboons will be studied for 10 weeks prepartum and 10 weeks postpartum, during which time behavioral and hormonal data will be collected. The levels of six hormones will be measured, including thyroid-stimulating hormone (TSH), free and total triiodothyronine (T3), free and total thyroxine (T4), cortisol, corticotropin (ACTH) and corticotropin- releasing hormone (CRH). Behavioral observations will result in measures of the duration and frequency of maternal and infant behavior, including activity, feeding, social behavior, maternal neglect, maternal abuse and infant distress. Analyses relating the mean levels of the physiological and behavioral measures will take into consideration any changes over time, particularly from pre- to postparturition. Results from this study will be of interest to those involved in research on reproductive endocrinology and affective disorders, and will be used to guide future research on the relationship between physiology and postpartum behavior.