Purpose : The purpose of this study was to assess the relative diagnostic capability of magnetic resonanceangiography(MRA) and CT angiography(CTA) in the evaluation of intracranial aneurysm. Materials and Methods : MRAand CTA were performed in 14 intracranial aneurysms (Including four which were ruptured) confirmed in the IIpatients involved by conventional angiography(CA). The size(in largest dimension) of the aneurysms ranged between3 mm and 20 mm and the mean was 10.5 mm. For MRA, the 3D TOF method, with magnetization transfer suppression, wasused at 1.5T. For CTA, twenty seconds after beginning the injection of contrast media(100mL with use of a powerinjector at the rate of 3 mL/sec), CT scanning(30-second exposure and 60-mm length) was performed with a tablespeed of 2 mm/sec and a section thickness of 2mm. The resulting data were reformatted by MIP. MRA and CTA werecompared with regard to the detection of aneurysms and their neck, size, shape, direction, intensity andrelationship to adjacent bony structures or vessels. Results : All aneurysms were clearly visualized with CTA. Inone case with a 3-mm aneurysm, however, this was not defined on MRA. Of the 13 aneurysms demonstrated by both MRAand CTA, eight were seen equally well with both modalities. CTA was considered to be superior to MRA in fivecases, either because calcification in the aneurysm wall was seen only on CTA(n = 3) or because the relationshipwith adjacent bony structures were seen better with CTA(n = 2). With CTA, the intensities of the aneurysm werehomogeneous in all cases ; with MRA, however, the intensities of three large aneurysms were different. Conclusion: MRA and CTA may be useful in the evaluation of intracranial aneurysm, CTA has specific advantages over MRA inthe evaluation of large aneurysms, calcification of aneurysm wall and relationship with adjacent bony structure.