We studied the clinical appearance and inheritance in five families with X-linked megalocornea. Affected male subjects had corneal diameters between 13.0 and 16.5 mm. Arcus juvenilis, mosaic corneal dystrophy, and cataracts were found only in adult affected male subjects. No carrier female abnormality was identified. The gene locus for the X-linked form is in the region Xq12-q26. This is near the locus described for Aarskog (facial-digital-genital) syndrome, Xq12-13.