Perinatal nutrition plays a fundamental role on the morphological organization and function of a number of brain stem structures. Because little is known of the effects of perinatal undernutrition upon sexually dimorphic structures underlying reproductive behavior, the locus coeruleus morphology of 60-day-old male and female Wistar rats was analyzed. Perinatal food deprivation until weaning significantly decreased the volume and neuronal number of locus coerulus in male and female rats, while nutritional rehabilitation ameliorated these alterations in males but not in females. Data suggest that perinatal undernutrition interferes with the neuroendocrine mechanisms underlying the establishment of sex differences of the locus coeruleus.