Five cases of a tumour in the quadrigeminal area have been described, 4 of which could be verified by autopsy. In 2 cases with a metastasis in the tegmentum of the mesencephalon, a Parinaud syndrome was present. In 2 other cases, however, with extensive destruction of the quadrigeminal plate and of the posterior commissure this syndrome was not present. In the 5th case, with a big vascular tumour of the pineal area, disturbances of eye movements and pupils were also lacking. From these observations we may conclude that (1) destruction of the quadrigeminal plate has no influence upon vertical eye movements. (2) destruction of the posterior commissure, in combination with the quadrigeminal plate, is not always followed by disturbances of vertical eye movements. In man it is still not clear which structures are responsible for the performance of vertical eye movements.