Serial disc photographs of 259 patients with elevated intraocular pressures were studied retrospectively up to 15 years. Twenty-nine eyes showed progressive enlargement of the optic cup. Early vertical extension of the cup occurred in vertical extension of the cup occurred in five eyes and horizontal extension in one. In 23 eyes, a generalized expansion of the cup (retaining its round appearance) was the first change observed, typically preceding visual field loss by several years. Thus, serial disc photographs are necessary for the earliest detection of optic nerve damage in ocular hypertension. Of 18 eyes with normal visual fields at the time progression of cupping was first noted, typical glaucomatous field loss developed in 50% during a follow-up of one to six years (average, two years). Therefore, treatment is indicated for eyes exhibiting progressive disc cupping, even in the absence of visual field defects.