A large body of experimental animal research on the neurotoxic effects of certain environmental chemicals provides evidence of a cascade of neurobehavioural effects including learning deficits, hyperactivity, anxiety, depression, lack of motivation, increased aggressiveness, altered maternal care and bonding, and an over-reaction to small stressors. For a number of years, scientific meetings and reports have recommended that assessing risk in chemical safety evaluations should include tests for developmental neurotoxicity (DNT) to uncover the potential of chemical substances to affect the developing brain. However, DNT testing has been required only in rare circumstances, and for some classes of neurotoxic pesticides. The role of developmental neurotoxicants as causative or contributory factors in children's learning and behavioural disorders warrants more attention in both research and policy.