Severe progressive ocular enlargement of late onset accompanying chronic uveitis and secondary glaucoma occurred in an 18-year-old man. Electron microscopy of the thin sclera from the unusually large eye (40x40x37 mm) disclosed collagen fibrils with mean widths that exceeded that of controls, but that were within the range of the fibril size typically present in the outer sclera. Thinner fibrils that normally occur particularly within the inner sclera were conspicuously absent. Morphologic observations on corneal and cutaneous collagen from the patient were unremarkable. No abnormality was detected on chemical analysis of cutaneous collagen. The abnormal morphologic pattern of the scleral collagen is interpreted as a probable arrest in scleral collagen synthesis.