The authors have presented their own series of 98 tumors of the lateral and third ventricles. The operations were performed by three surgeons during the last fifteen years at the Department of Neurosurgery in Brno. Thirty-two lesions were localized in the third ventricle. Primary tumors involved 8 colloid cysts, 6 meningiomas, 4 hamartomas, 3 plexus papillomas. Secondary tumors were 11 tumors mostly from the thalamus. Suprasellar tumors growing against the floor of the third ventricle are not included in the series. Surgical approaches: at the beginning only transventricular approach according to Bush was used. It is the approach via the gyrus frontalis medius to the lateral ventricle and through the foramen Monroe to the third ventricle. After finding the positive features of the transcallosal interhemispheric approach only this approach was used. Nevertheless, the authors soon found out that it was impossible in some cases. The aim of this study is to show in which cases it is better to use transcallosal or transventricular approach. In short, solid tumors (meningiomas) bigger than three cm in diameter are not suitable for the transcallosal approach.

        Key words: tumor of the third ventricle, operative approaches