Tumors are only rarely found in the lateral ventricles. Although various oncotypes of these tumors differ in growth rate and invasiveness they present the same clinical pattern with the same diagnostic and surgical problems. Thus we can consider them as a group. This series comprises 51 primary tumors arising strictly from the structures of the lateral ventricles, the majority from the trigone, operated on between 1952 and 1988: 20 meningiomas, 19 ependymomas, 9 papillomas of the choroid plexuses, and 3 subependymomas. As most of these tumors were benign, the response to surgical treatment was, as other authors have found, good with permanent cure or long survival in the majority of cases. Advances in neuroradiological techniques have greatly facilitated the work-up and differential diagnosis of these tumors. Of the various surgical approaches, the parieto-occipital is preferred by our department, even for tumors of the dominant hemisphere. Our operative mortality of 10.6% tallies with that of other workers.