140 patients from 8 countries with granular corneal dystrophy Groenouw type I are described, and 21 slit-lamp photographs demonstrate inter-familial differences and intra-familial similarities. The clinical appearance varied from mild, with only a few granules on the cornea, to a monstrous course with an almost opaque cornea. The following diagnostic criteria are suggested for the disease, as these signs are described in extensively quoted key references and meet the descriptions in most papers on this subject: Dominant inheritance, as well as 1) typical slit-lamp appearance and/or 2) granules that stain with Masson trichrome histologically, and/or 3) rod-shaped bodies seen electron microscopically.