Neurovascular compressive sites at the root entry zone of the trigeminal nerve were investigated in 25 patients with trigeminal neuralgia by using the fine three-dimensional (3D) magnetic resonance (MR) angiogram, obtained by a 3D time-of-flight, spoiled gradient-recalled sequence. The characteristic 3D MR angiographic findings of the offending vessels were obtained at the neurovascular compressive sites 19/23 (83%), including intermittent MR signal intensity within the vessels in 14/23 (61%), and unclear margin of the vessels in 5/23 (22%). Those abnormal 3D MR angiographic findings were commonly observed at the site of neurovascular compression in conjunction with moderate degree (grade II) and severe degree (grade III) in 19/20 (95%) of the actual nerve compression by the offending vessels. Abnormal findings with 3D MR angiograms may provide flow-related information to suggest a certain neurovascular compression upon the trigeminal nerve by the offending vessels. Those novel 3D MR angiographic findings may be useful for the diagnosis and decision-making process to execute the microvascular decompression surgery in patients with trigeminal neuralgia.