High risk/recurrent CNS tumors have a poor prognosis. We studied tandem high dose chemotherapy (HDC) with hematopoietic progenitor stem cell rescues (HPCR) as potentially curative therapy. Twenty-four patients (mean age 6.8 years) were enrolled, 19 underwent HDC/HPCR. Diagnoses were medulloblastoma (n = 9), germ cell tumor (n = 4), high grade astrocytoma (n = 2), supratentorial PNET (n = 1), pineoblastoma (n = 2), or papillary meningioma (n = 1). Cytoreduction regimen #1 consisted of carboplatin (500 mg/m(2)) x 3 days, etoposide (250 mg/m(2)) x 3 days, and thiotepa (300 mg/m(2)) x 3 days. Patients without progression or excessive toxicity (n = 11), received regimen #2 with melphalan (60 mg/m(2)) x 3 days and cyclophosphamide (1,500 mg/m(2)) x 4 days. Projected overall/event-free survival for the 19 patients was 51/37% and 34/28% at 1 and 5 years, respectively. Toxicity was significant with six treatment related deaths including four with veno-occlusive disease. This regimen of sequential HDC/HPCR in high risk/recurrent CNS tumor patients is not feasible due to toxicity.