The authors report a case in which a germinoma in the pineal body displayed spontaneous regression after placement of a ventriculoperitoneal (VP) shunt. Spontaneous regression of malignant tumors is extremely rare, occurring in only one of 60,000 to 100,000 patients. Although in rare cases spontaneous regression is known to occur in patients with testicular seminomas, only one case of spontaneous regression of a primary pineal germinoma has so far been reported. In the present case a 17-year-old man presented with headache. A tumor in the pineal body and acute hydrocephalus were revealed by head computerized tomography (CT) and magnetic resonance (MR) imaging, and VP shunt placement was performed. Computerized tomography scanning of the head was performed four times during a 2-week period following the operation, and the patient was temporarily discharged to return to school. At the time of discharge, CT scanning demonstrated no change in the size of the tumor. Two months later, the patient was readmitted to the hospital to undergo surgery. At that time, head MR imaging revealed regression of the tumor. The pathological diagnosis of the lesion was germinoma. The patient underwent three courses of chemotherapy, during which carboplatin and etoposide were administered, in addition to a 24-Gy dose of radiotherapy. No manifestations of nerve impairment were noticed, and the patient was observed on an outpatient basis. The authors think that the factors involved in tumor regression included the effects of the VP shunt, the effects of radiation absorbed during head CT scanning, and the role of the patient's own immune response. However, no conclusion has been reached concerning the actual cause.