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 of surgery-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.