BACKGROUND : Intraventricular trigonal meningiomas (ITM) seem to have a tendency for extensive perifocal edema formation following radiosurgery (RS). To further investigate this hypothesis, we undertook the following study. METHODS : We retrospectively reviewed records of patients who underwent RS for intraventricular meningiomas at our institution. RESULTS : From 1999 until 2019, 5 patients underwent single-session RS as primary treatment for ITM. Patients were treated either with a Gamma Knife or a CyberKnife. The mean prescription dose (PD) was 13.0 Gy ± 0.9, the mean tumor volume was 5.8 cc ± 3.1, and the mean follow-up (FU) was 8.9 years ± 5.6. Perifocal edema developed in 4/5 patients after a mean interval of 6.4 months ± 1.2. It was symptomatic in 2/5 patients. The edema regressed spontaneously in 4/5 patients. One of the patients underwent RS for the same ITM twice. One patient's edema was treated medically with steroids, and none of the patients underwent surgery following RS. CONCLUSIONS : Even though the number of patients is low, there seems to be a comparably high risk for the formation of a perifocal edema following RS for ITM. Single-session RS as primary treatment for ITM seems to be safe and effective even though a perifocal edema is likely to develop. The perifocal edema and the ensuing neurological deficits were transient and could be managed conservatively in all of our 5 cases.