Magnetic resonance imaging (MRI) was used to monitor cyclosporine therapy for chronic progressive multiple sclerosis in a multicenter clinical trial and an analysis was performed to determine whether there was a correlation between clinical changes and MRI changes. MRI was performed on 163 patients at the onset and completion of the 2-year study. Burden of disease (BOD, lesion load) was quantitated by a single observer using a computer program. Active lesions were also identified. The Expanded Disability Status Scale (EDSS) score was determined every 3 months MRI data did not show any effect of cyclosporine treatment on BOD progression (mean 24.5% increase/yr) or lesion activity. However, there was a statistically significant positive correlation between the baseline total BOD value and the baseline EDSS score (r = 0.221, p = 0.005) and a positive correlation between the percent changes in BOD from baseline to exit and EDSS score (r = 0.186, p = 0.018). The study supports the concepts that MRI is a useful technique in monitoring therapeutic trials and that MRI is a direct measure of pathology.