Fourteen members of four families with fleck systrophy of the corneal stroma were examined and studied. Corneal and lens changes were noted in all patients. Corneal sensation was normal. Corneal biopsies were performed on two patients and a corneal button of a patient with fleck dystrophy and keratoconus was studied. Light and electron microscopy and histochemical studies showed this dystrophy to consist of abnormal keratocytes with variable numbers of membrane-limited intracytoplasmic vacuoles containing a granular to fibrogranular material that stains positively for mucopolysaccharide. This appears to be the first reported incidence of a dominantly inherited disorder of mucopolysaccharides affecting the eyes.