The authors analyze the results of surgical treatment of 51 consecutive patients with colloid cysts of the third ventricle. Patients were operated by the senior author from 1981 to 1996. Provided are the clinical signs, CT and MRI diagnostic criteria. Surgical treatment of colloid cysts is discussed in every detail. The authors believe, transcallosal approach with cyst enucleation via foramen of Monroe is the most adequate technique. No complications related to surgery were observed, except for transitory fixational amnesia, which completely regressed by 2-3 weeks postoperatively. The conclusion is that transcallosal approach with subsequent removal of the colloid cyst via the foramen of Monroe is a safe and reliable technique bringing no surgical complications.