The most frequent cause of trigeminal neuralgia is arterial compression, which can be caused by venous compression, tumor, or arachnoid adhesion. In our hospital, both plain and contrast-enhanced MRIs are taken for patients with trigeminal neuralgia. Furthermore, Gamma Plan^®, a software for Gamma knife surgery, is adopted for creating a 3-dimensional image around the trigeminal nerve. The author reports 3 patients with trigeminal neuralgia caused by venous compression, which was confirmed by surgery. The 3 were from 114 patients with intractable trigeminal neuralgia. Some patients with trigeminal neuralgia caused by venous compression do not have typical lancinating pain, and plain MRI rarely detects small paraneural veins. Transposition of the responsible vein is frequently difficult when the vessel joins the superior petrosal sinus. Physicians should suspect venous compression in patients whose MRIs reveal no typical arterial compression.