Pregnant sows were administered trichlorfon (Neguvon®) during gestation. Examination of the offspring revealed clinical symptoms which included ataxia and tremor. The weights of the cerebrum and the celebellum were significantly reduced (67% and 41% of the control values). There was a clear correlation between the decrease in total brain weight and decrease in cerebellar weight (r = 0.94). Histological examination showed a well preserved lamination of the cerebral and cerebellar cortex. Periodical loss of Purkinje cells was the most notable finding in the cerebellum. The molecular layer in such regions was markedly thinned. Neurochemical investigations of the cerebellum showed a significant decrease in specific activity of the transmitter synthesizing enzymes choline acetyltransferase, glutamate decarboxylase and aromatic amino acid decarboxylase (61.6%, 30.3% and 47.1% of the control values, respectively). No effect in high affinity D-aspartate uptake was observed.