The aim of this study was to investigate the effects of an early olfactory deprivation on novelty-seeking behavior and lymphoid organs during post-natal development in rats. Therefore, we performed a bilateral nasal obstruction on 8-day-old rats and we studied its effects at 21 days of age. Animals exposed to nasal obstruction presented an increased plasma corticosterone level, an adrenal hypertrophy more marked in females (+68% in females and +29% in males compared to sham group), a reduced growth of olfactory bulbs only in females (-43% compared to sham group) and an impaired novelty-seeking behavior, which seemed also more marked in females. Moreover, thymus specific weight and ConA-induced proliferative activity of thymocytes were diminished after induction of nasal obstruction in females but not in males. At last, spleen specific weight was not affected by nasal obstruction, although mitogen-induced proliferative activity of splenocytes was diminished in both sexes. These data showed that early olfactory deprivation by nasal obstruction was associated with some behavioral, endocrine and immunological alterations, which may have serious consequences for the health and the social status of the individuals.