Offspring of rats given oral doses of Saline or Imipramine (5 mg/kg) from 14-21 days prior to mating till parturition were reared, after weaning, in deprived or enriched environments. At 25-27 days and at 80-83 days the home cage behaviour of the Ss reared in the enriched environment was observed. Histological measures of brain development in both the deprived and enriched Ss were taken at the conclusion of behavioural observations. The Imipramine exposed offspring failed to show the characteristic histological changes associated with enriched rearing conditions. In addition they were behaviourally unresponsive and spent significantly less time than the Saline offspring interacting with other animals and the environment. It was argued that the physiological and behavioural unresponsiveness of the Imipramine offspring was due to a subtle teratogenic effect which prevented the Ss from interacting with the environment.