Five infantile and one adult case of Sturge-Weber disease were studied pathologically. The calcification occurring under the leptomeningeal angiomatosis increased with advancing age. Light and electron microscopy of two cases showed the smallest, and therefore possibly the earliest, calcifications occurred in perithelial cells. It is hypothesized the cause of calcification is anoxic injury to endothelial, perithelial and possibly glial mitochondria due to stasis and abnormal vessel permeability in the cerebral vessels composing the Sturge-Weber angioma.