The effect of D-penicillamine (DPA), a copper chelator, on the cerebellar maturation of the offspring of pregnant rats is evaluated. Pups of the mothers which received DPA in a daily dose of 300-400 mg during their last six days of gestation, showed an appreciable decrease in body and cerebellum weights, and cerebellar degenerative changes on histological examination. A postnatal diet DPA-free given to lactating mothers appeared to have a significant effect in reversing the cerebellar degenerative changes in their offspring.