Purpose : To determine the usefulness of MR imaging and MR angiography (MRA) in the evaluation of patientswith hemifacial spasm. Material and Methods : One hundred and twenty-five patients with hemifacial spasm wereincluded in this study. Axial T1-, T2-weighted images, proton density image (3mm thickness, 256x192) and 3-D TOFMRA were performed. Relation between facial nerve and adjacent arterial structures was carefully evaluated, whichwas correlated with surgical findings. Results : MRA identified the presence of offending vessels at the root exitzone of facial nerve and its origin in 117 patients(52 PICA, 50 AICA, 6 vertebral artery, 9 dual vessels). Therewere 4 false negatives and 4 false positives. Vascular groove at the root exit zone was identified in 52 cases,but there was no positive correlation between severity and duration of symptoms. The presence of ipsilateral orcontralateral distal loop formation of vertebral artery were noted in 63 patients. In addition, 4 cases ofneoplastic and vascular lesions were also demonstrated on MR imaging. Conclusion : Combination of MR imaging andMRA is an useful screening modality in the presurgical evaluation of hemifacial spasm, which can demonstrate theoffending vessels as well as other pathologic lesions.