In order to help avoid complications of parotid surgery, we investigated the relationship between the facial nerve and the retromandibular vein. Fifty dissections were performed on 30 cadavers. In 45 (90%) of the cases the retromandibular vein was located on the medial side of the upper and lower trunks of the facial nerve, and in 5 (10%), the course of the retromandibular vein was lateral to the lower trunks and medial to the upper trunks. These variations were divided into subgroups. The most commonly encountered variation was that the retromandibular vein crossed the facial nerve from the medial (34 cases) or lateral side (3 cases) at a point between the bifurcation and ramification points of the lower facial trunk. In one case, the retromandibular vein was detected on the lateral side of the facial nerve at the bifurcation. In 3 cases (15%), the course of the retromandibular vein was different on the right and left sides of the face in the same cadaver.