The potential role of magnetic resonance angiography (MRA) in clinical neurosurgical practice was evaluated in 150 consecutive patients in an attempt to define clinical situations in which it aided in diagnosis, helped guide treatment options, and/or possibly eliminated the need for conventional catheter angiography. Among patients with nonvascular pathology (n = 42), MRA provided useful clinical information in 55% of cases, and could have effectively replaced catheter angiography in 76% of cases. In this group of patients, MRA provided excellent depiction of tumour and vessel relationships, and in conjunction with conventional imaging modalities reliably ruled out the question of tumour versus aneurysm whenever that question was raised. Among patients with vascular lesions (n = 108), MRA visualized the lesion in 18 of 20 (90%) aneurysms, 11 of 11 (100%) vascular malformations, 31 or 31 (100%) cases with known occlusive vascular disease, and reliably excluded occlusive vascular disease in 19 of 30 (63%) cases. The MRA potentially could have replaced conventional catheter angiography in less than 8% of cases with vascular pathology treated surgically, and in 76% of cases with vascular pathology treated medically or expectantly. Imaging time was relatively short, 10 to 20 minutes for intracranial vessels and 6.5 to 13 minutes for extracranial vessels. Shortcomings included the lack of spacial resolution required for surgical planning and the possible misleading information in the settings of low flow and partial thrombosis. It is concluded that currently available MRA modalities contribute useful information in a wide spectrum of neurosurgical clinical situations including screening and serial follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)