OBJECTIVE A spectrum of both radiosensitive and radio-resistant lesions occurs in the region of the posterior third ventricle (PTV). Most of these are associated with hydrocephalus requiring a cerebrospinal fluid diversion procedure. The present study aims to assess the effectiveness of endoscopic biopsy and third ventriculostomy (ETV) in these patients. METHODS Twenty-four patients with PTV lesions with moderate to severe hydrocephalus were managed prospectively. All patients underwent ETV and biopsy of the lesion during the same procedure. The ETV could be performed in all patients, where as in 23, a successful biopsy could be obtained. The ETV was successful in 22 patients; it failed in 2 patients requiring shunt insertion. A positive biopsy was obtained in all the patients (pinealocytoma 4, pinealoblastoma 10, embryonal cell carcinoma 1, germinoma 2, oligodendroglioma 1, astrocytoma 2, tuberculoma 4). All patients were subsequently managed with further surgery, radiation, and chemotherapy either alone or in combination depending on the pathology. One patient with a tumor bed hematoma required clot evacuation. The follow-up period ranged from 12 to 36 months. Two patients died, one during hospital stay with a tumor bed hematoma and another at 6 months follow-up due to extensive leptomeningeal spread. CONCLUSIONS The high yield of endoscopic biopsy (100%) and success of ETV (91%) emphasizes its role in management of the diverse group of PTV lesions in arriving at the optimal definitive management.