Two patients-6 and 14 years old-with tuberous sclerosis are presented. Both developed a subependymal giant cell astrocytoma from nodules located near to the foramen of Monro. They caused obstruction of the cerebrospinal fluid pathways. Signs of raised intracranial pressure were detected in both patients, and one of them had also developed infantile spasm-Blitz-Nick-Salaam seizures. Cutaneous stigmata being characteristic for this entity were observed in both cases, but their mental development was unaffected. Diagnosis was based on computed tomography. Angiography did not reveal pathological vessels. The tumours were completely excised through transcallosal exposure in both cases. The patients have been symptom-free during the follow-up time of 1 and 2 years. Although the incidence of malignant transformation of tuberous sclerosis is less than 15% the disease generally has a poor prognosis which can be ascribed to sudden increase of intracranial pressure caused by obstruction of cerebrospinal fluid pathways by paraventricular tumours. However, regular follow-up of paraventricular nodules and maintenance of patency of cerebrospinal fluid pathways by microsurgical methods in patients suffering from mild cerebral disorders offers a better chance of survival.