Pre- and postweaning measures of learning and locomotor activity were used as indices of CNS function after early perinatal neurotoxic insult. Triethyltin administered on Postnatal Dat 5 (PND5) was used as the neurotoxicant. Learning deficits and alterations in locomotor activity were observed during both the pre- and postweaning periods. Preweaning learning ability was evaluated with an appetitive alleyway paradigm, while an automated radial-arm maze (RAM) was used to assess juvenile learning. Preweaning open-field locomotion was evaluated in the presence and absence of home-cage litter while postweaning activity was measured in an automated device, the Motron, or as a component of performance in the RAM.