The authors report the anatomical pathological findings collected from 1979 to 1992 in a series of 350 consecutive patients referred because of apparently idiopathic trigeminal neuralgia (TN) and operated on using a microsurgical keyhole approach of the cerebellopontine angle. In 20 cases (5.7%) the cause of the TN was a tumor or a vascular malformation, in 8 (2.3%) an atherosclerotic huge vertebrobasilar artery, all actually corresponding to symptomatic TN. Among the 322 others (= real idiopathic TN), only 10 (3.1%) had no visible compressive factor whilst 312 (96.9%) had one (or several) conflicting vessel(s): superior cerebellar artery in 90%, anterior inferior cerebellar artery in 23.6%, and a vein in 24.7%. In 35.7% of the patients, several neurovascular compressions (NVC) were found in association. Site(s) along the root, location around its surface and degree of severity of the conflicts were carefully studied. Of prime importance is the fact that, beside the localized lesions due to the NVC(s), a moderate to marked global atrophy of the entire root was frequently seen (in 67% of the cases) indicating that the NVC might not be the sole pathogenetic agent of the disease.