The purpose of this study was to determine the efficacy of endoscopic treatment in patients with intraventricular tumors. A series of 30 patients with endoscopically treated intraventricular lesions is reported. The lesions included seven colloid cysts, six astrocytomas, three subependymomas, two ependymomas, and one each of the following: pineoblastoma, pineocytoma/pineoblastoma (intermediate type), epidermoid cyst, pineal cyst, medulloblastoma, arteriovenous hemangioma, cavernoma, choroid plexus papilloma, pituitary adenoma, craniopharyngioma, melanoma, and germinoma. Total tumor resections, partial resections, biopsies, stent implantations, septostomies, and third ventriculostomies were performed. In two cases (two subependymomas > 2 cm in diameter), piecemeal endoscopic resection was ineffective because of the very firm consistency of the tumors. Therefore the endoscopic procedure was discontinued and the tumors were removed microsurgically. In the remaining cases the procedures were completed as planned. Even in the presence of difficulties such as poor orientation or significant bleeding, there was no need to abandon the endoscopic procedure. A total of 28 strictly endoscopic interventions were performed, in which the average duration was 85 minutes (range 35-170 minutes). All colloid cysts and the epidermoid lesion were completely evacuated and the capsules were widely resected. Total extirpation of solid tumors was achieved in five cases, whereas most astrocytomas were partially resected. The hydrocephalus-related symptoms resolved in all of the 22 patients with cerebrospinal fluid pathway obstruction. There were no endoscopy-related deaths. In two cases, major bleeding occurred and was controlled endoscopically. The authors observed one case of meningitis, one of mutism, two of memory loss attributed to forniceal injury, one of transient trochlear palsy after a biopsy specimen of an aqueductal tumor was obtained, and one of transient confusion after a biopsy specimen of a germinoma was obtained. In the authors' preliminary experience, the endoscopic approach was found to be safe and effective. In this series, it was possible to achieve relief of noncommunicating hydrocephalus, tumor resections, and even complete tumor removals by using endoscopic techniques. Based on the results, the authors believe that endoscopic techniques should be considered in the treatment of selected intraventricular lesions.