Summary: The objective of this paper is to compare the diagnostic efficacy of 3 DFT time-of-flight MR angiography (MRA) at middle-field-strength and high-field-strength in diagnosis of intracranial aneurysms.Thirty-one patients, including 26 patients with angiographically confirmed intracranial aneurysms (n = 28), underwent MRA at 0.5 and 1.5 T. Images were interpreted by six trained observers who were blinded to diagnosis. Twelve projections of MRA of the circle of Willis, by maximum-intensity projection algorithm, were reviewed using continuous confidence-judgment scales.It was found that MRA at 1.5 T was more sensitive than that at 0.5 T in detection of aneurysms. The sensitivity of six observers ranged between 50 and 64\% (mean 56\%) at 0.5 T, and between 61 and 86\% (mean 75\%) at 1.5 T. In the smaller aneurysms less than 5 mm, the differences between the units became greater. The sensitivity for small aneurysms ranged from 23 to 54\% (mean 32\%) at 0.5 T, and from 31 to 69\% (mean 58\%) at 1.5 T.Our conclusion was that high field strength confers higher accuracy in the detection of intracranial aneurysms with MRA with current-generation MR imagers. (Copyright 2004 ScienceDirect)