Colloid cysts may be found in any part of the third ventricle. The authors report that four out of 12 patients with colloid cysts of the third ventricle suffered acute neurological deterioration, and unilateral ventriculostomy resulted in dramatic recovery in two patients. Unilateral ventriculostomy followed by clinical assessment and computed tomographic scanning is an acceptable approach in emergency situations; computed tomographic scanning allows early detection of third ventricular colloid cysts. Ventriculoperitoneal shunting provides a laternative measure to surgical removal of the cyst. Definitive management soon after diagnosis and before acute neurological deterioration is recommended. The cases presenting with sudden death in the literature are reviewed.