PURPOSE: To evaluate MRI findings of Guillain-Barre syndrome. MATERIALS AND METHODS: In six patients with Guillain-Barre syndrome diagnosed by clinical, cerebrospinal fluid and electrophysiologic findings, a retrospective review of MR findings was conducted. Follow-up MRI scans were carried out in two patients showing minimal clinical improvement. RESULTS: Marked or moderate enhancement of thickened nerve roots was seen in all cases on gadopentetate dimeglumine enhanced axial T1-weighted images. Two patterns were seen ; one was even enhancement of both anterior and posterior nerve roots (n=1) and the other was enhancement of anterior nerve roots only (n=5). Enhancement and thickness of nerve roots was seen to have slightly decreased on MRI follow-up at 32 and 50 days ; clinical and electrophysiologic examination showed minimal improvement. CONCLUSION: Although MRI findings of nerve root enhancement are nonspecific and can be seen in neoplastic and other inflammatory diseases, the enhancement of thickened anterior nerve roots within thecal sac suggests Guillain-Barre syndrome.