OBJECTIVE: Choroid plexus cysts are common in the developing fetus, and although often persisting into adulthood, they rarely represent the underlying cause of symptomatic unilateral ventriculomegaly. The case presented here highlights both the diagnostic obscurity and endoscopic management of a choroid plexus cyst in a symptomatic patient. CLINICAL PRESENTATION: The patient is a 47-year-old white woman who presented with acute exacerbation of debilitating, diffuse, and postural headache, nausea, vomiting, early papilledema, and short-term memory loss. Cranial magnetic resonance imaging revealed an intraventricular mass obstructing the foramen of Monro on the left with ventriculomegaly. Cranial computed tomographic imaging demonstrated unilateral ventricular enlargement. INTERVENTION: During stereotactic endoscopic exploration, a choroid plexus cyst was evident at the foramen of Monro. Endoscopic cauterization of the cyst resulted in a decrease in the size of the left lateral ventricle, with complete relief of the patient's headaches and resolution of her memory loss. She remained headache free at the time of a 3-year follow-up evaluation after surgery. CONCLUSION: Choroid plexus cysts remain a diagnostic challenge; their presence should be sought out in the face of ventricular asymmetry and symptomatic hydrocephalus. Endoscopic ablation offers a minimally invasive treatment for the management of these lesions.