Background: The aim of this study of third ventricular colloid cysts (TVCC) from a defined population was to estimate the incidence, the presenting features, the surgical treatment, the treatment related complications, and the clinical and surgical outcomes. Methods: A reprospective study of 32 consecutive primary surgeries for TVCC was performed at Oslo University Hospital in the time period 2002-2015. Results: The estimated incidence rate for TVCC was 0.9 per million. Mean age was 41 years and the male-to-female ratio was 1: 1.5. The most common presenting symptoms were headache (100%), ataxia (25%), reduced level of consciousness (22%), and impaired vision (19%). The surgical mortality was 0%. Gross total resection (GTR) was achieved in 69% based on intraoperative findings and in 81% based on postoperative imaging. The rate ofsurgery--related complications was 13%. There was no statistically significant difference between microsurgery and endoscopic surgery with respect to surgery-related complications and grade of resection. At time of follow-up, all patients were able to care for themselves. Conclusions: Due to the risk of acute neurological deterioration and sudden death, surgical treatment is recommended for patients with symptomatic TVCC. This study shows that surgical resection can be performed with a fairly low risk and with a good long-term outcome.