BACKGROUND Once it was confirmed that magnetic resonance imaging (MRI) including angiography (MRA) could demonstrate intracranial aneurysms, a study was set up to establish whether satisfactory images could be obtained to plan and execute early surgery on ruptured intracranial aneurysms without recourse to intra-arterial digital subtraction angiography (IA.DSA) in the acute phase of the illness. METHODS All patients presenting with a subarachnoid haemorrhage (SAH) were considered for MR studies. The patient selection was based on whether they were considered fit enough to tolerate scanning and did not have a known contraindication. A standard protocol was used--a three-dimensional time-of-flight with T1 and T2-weighted sagittal and axial images. If an aneurysm was demonstrated and early surgery was undertaken they were entered into the study. RESULTS Over a 25-month period, 122 patients were submitted for MR studies, these being selected from over 200 patients presenting with an SAH. Aneurysms were believed to be present in 55 patients who were clinically suitable for early surgery. There were 21 males and 34 females, with an age range of 23-79 years, a mean of 50.5 years. Sixty-three aneurysms in all were demonstrated and 55 of these were surgically dealt with. There were two false positives. CONCLUSIONS MRI is the investigation of choice to plan surgery in those patients presenting with an SAH who, on clinical grounds, would be considered suitable for early surgery. The imaging is easily obtained, non-invasive, avoids radiation, and in view of the multiple images obtained is often superior to conventional DSA.