Acase of posterior internuclear ophthalmoplegia with bilateral and asymetric manifestations in a patient with subacute combined degeneration of the spinal cord is reported. The diagnosis of the spinal cord disease was made in clinical findings and proved by absorption of radioactive cyanocobalamin through the Schilling's urinary excretion test. The electromyogram of the left medial rectus muscle showed no signs of paresis such as are found in lower motor disease or myopathies.