40 patients with multiple sclerosis were investigated by magnetic resonance imaging (MRI) and computer tomography (CT). Additionally, cerebrospinal fluid (CSF) findings and evoked potentials (EPs; visual, brainstem) were evaluated. MRI findings were abnormal in 85% of the patients, whilst CT scan showed pathological changes in only 23%. The sensitivity for detecting lesions was significantly higher for MRI than CT. 86% of 23 patients with a duration of disease of more than 1 year had pathological MRI findings, and MRI was abnormal in 82% of 17 patients with a duration of symptoms up to 1 year. All patients with abnormal MRI had at least one other pathological laboratory finding. CT revealed only large lesions, and in patients with abnormal CT MRI visualized lesions more extensively. Additionally, brainstem lesions could be verified in 6 patients and spinal cord lesions in 3 cases. CSF was abnormal in 86%, and positive MRI findings occurred in 26 of 31 patients with abnormal CSF. Abnormalities of EPs were found in 76%, and MRI was positive in 24 of 33 patients with abnormal EPs.