Between 1973 and 1987 a total of 38 patients with midbrain lesions were encountered. In 15 cases surgical exploration was not warranted, 23 patients underwent definitive surgical exploration. The infratentorial supracerebellar approach proved to be the ideal route for the exposure of the 21 lesions which were located in the more dorsal aspect of the midbrain; in 7 cases the extension of the mass lesion reached from the cerebellum into the midbrain and, therefore, the exposure demanded a transcerebellar route. In one case with a hamartoma in the interpeduncular cistern and another case of a metastasis of the right cerebral peduncle the subtemporal approach was chosen. Three patients died as a consequence of the operation, but in the other 20 there was no increase in morbidity after surgery and the immediate postoperative course was favourable. Four cases with malignant tumours died from recurrence despite radiotherapy. The remaining 16 cases have been doing well up to 14 years after surgery.