This study was performed to evaluate the correlation between changes of cross-sectional cord area and disability in multiple sclerosis. Axial magnetic resonance images at the C-5 spinal level were obtained at entry and 12 months later for 29 patients with clinically definite multiple sclerosis. The degree of disability was inversely correlated at entry and follow-up with the cross-sectional area and the transverse diameter of the spinal cord. In addition, changes in disability correlated inversely with changes in cross-sectional area (r = -0.4, p = 0.04). These findings suggest that cross-sectional cord area at C-5 might be a useful marker of disease evolution.