PURPOSE: The aim of our study was to evaluate the usefulness of MR imaging in cases of traumatic brachial plexus injury. MATERIALS AND METHODS: We evaluated 25 patients with traumatic brachial plexus injury as seen on MR images prior to surgical exploration and repair. MR images were retrospectively evaluated for nerve root avulsion and pseudomeningocele, and postganglionic lesions. Results were correlated with final diagnosis after surgical exploration . RESULTS: One hundred and four of 125 root levels (83%) were adequately imaged. Neve root avulsion was shown at 28 levels(54%). Avulsion with or without pseudomeningocele was seen at 37 levels(71%)(80% sensitivity, 91% specificity). The presence of ten of 12 postganglionic lesions (83%) was revealed by MR imaging. CONCLUSION: MR imaging is valuable for revealing preganglionic nerve root avulsion in patients with traumatic brachial plexus injury or postganglionic lesions.