Colpocephaly is a congenital abnormality in the ventricular system of the brain. The radiological diagnosis is usually made in the perinatal period and later presages intellectual disability. Adult cases of newly diagnosed colpocephaly have only rarely been reported. We have studied an adult with massive colpocephaly who is an otherwise functional woman. The diagnosis should be considered in patients with ventriculomegaly disproportionately affecting the occipital horns and must be differentiated from the more common form of adult ventriculomegaly-idiopathic normal pressure hydrocephalus (NPH).