This paper is a retrospective review of all patients treated for a colloid cyst of the third ventricle at Royal Prince Alfred Hospital over an 18-year consecutive period. Our experience is fairly typical compared with other published series. Colloid cysts made up 1.6% of tumours treated by the neurosurgical unit. Patients presented with non-specific neurological symptoms and signs, commonly suggestive of raised intracranial pressure. Microsurgical excision was carried out via the transcallosal route in 34 cases and the transfrontal approach in four cases. There was no apparent difference in results from the different surgical approaches. In 86% of patients reviewed after more than 6 months good long term outcome was achieved. These benign tumours can be safely cured if the diagnosis is made early and the cyst removed by careful microsurgical techniques.