The authors report 12 cases of neurological syndromes due to folic acid deficiency, due in 8 cases to chronic alcoholism. In 5 cases there was polyneuritis, 3 cases had cerebellar atrophy, whilst 4 patients had subacute combined degeneration of the cord. Folic acid deficiency occurred alone in five cases out of twelve, as in 3 cases vitamin B1 deficiency was associated, and in four cases there was malabsorption of vitamin B12. A neuropathological study of these cases showed: 1) moderate involvement of the mamillary tubercles as observed in deficiency encephalopathies. 2) severe peripheral nerve involvement especially of axonal type. 3) involvement of the anterior horns of the spinal cord with appearances of central chromatolysis and a few atrophic neurones.