The relationship between the thickness of the myelin sheath and the square area of the axon was measured in both short-term and long-term remyelinated axons following demyelination in the central nervous system, and compared with that of controls. The normal linear relationship between thickness of myelin sheath and axon size was not present in either group of remyelinated axons even though there was a trend, not statistically significant, in the long-term remyelinated animals to approach that of normal animals.