The pituitary-adrenal response of mother and infant squirrel monkeys was assessed under basal conditions and after 5, 10, or 20 min of separation followed by 30 min of reunion. All separation conditions produced equal increments of cortisol (approximately 50%) in both mothers and infants. These increments were lower than would have occurred in the absence of reunion. These results extend previous reports that reunion ameliorates the psychoendocrine effects of separation and indicate that mother-infant attachment can be studied with shorter periods of separation than have been used customarily.