Snow-capped teeth (SCT) is a rare form of amelogenesis imperfecta, hypomaturation type. It has been alluded to on numerous occasions but, to our knowledge, no pedigree or clinical-histopathologic data have been published. In this report, two families are described. Scanning electron microscopic (SEM) studies of unetched teeth from affected persons revealed numerous defects of the enamel surface. After etching with 10 percent hydrochloric acid for 21/2 minutes to remove the outer prismless layer of enamel, SEM features of the enamel prism were essentially identical to those of normal teeth. These findings suggest that the structural defect in SCT is confined to the outer prismless enamel layer and that the bulk of the enamel is normal. The genetic analysis supports the concept that SCT is inherited in an X-linked recessive fashion and not as an autosomal dominant trait, as previously reported.