Management of the obstructive hydrocephalus that accompanies tumors located in the third ventricle has traditionally involved either urgent tumor resection, with resultant ventricular decompression, or cerebrospinal fluid diversion that requires either ventriculostomy or shunt placement prior to tumor removal. Although this approach has worked well for the better part of a century, it has both short- and long-term sequelae that can possibly be avoided. Beacause a number of lesions in this area are benign or are amenable to radiotherapy, a less invasive approach to their treatment is desirable. The advances in both instrumentation and techniques of endoscopic surgery have established alternatives to the traditional treatment of third ventricular tumors and resultant hydrocephalus. The authors review the treatment of 19 patients with posterior third ventricular tumors who presented to Arkansas Children's Hospital over a 5-year period (September 1993-July 1999). In 11 patients signs and/or symptoms of hydrocephalus were demonstrated and were treated with endoscopic third ventriculostomy, additionally, a biopsy procedure, resection, or fenestration of the tumor was performed in a number of patients. Endoscopy was believed to have been of benefit in all patients, despite the eventual failure of the ventriculostomy in one patient. There were no complications in this series. The algorithm thus developed by the authors provides both a diagnostic and therapeutic pathway that may ultimately reduce the morbidity associated with the treatment of patients with posterior third ventricular lesions.