The aim of the present study was to test the hypothesis that exposure to neonatal and/or juvenile stress results in distinct persisting modification of adult male rats' emotional and social competence. Compared to non-stressed control rats, neonatally stressed rats and rats exposed to combined neonatal and juvenile stress, had reduced frequency and duration of social encounters, and lower anxiety levels. Juvenile stress alone, induced more frequent, but shorter social encounters in adulthood. No significant differences in aggressive behavior were found between any of the groups. The findings confirm the existence of developmental time windows during which exposure to unpredictable stress can affect adult emotional and social behavior without affecting cognitive function. (c) 2008 Elsevier B.V. All rights reserved.