The Hoskins' gonioscopic classification of developmental glaucoma is useful in choice of therapy and in prognosis. It is based on the alterations occurring in the iris, the cornea and the trabecular meshwork. The various syndromes are described by the various combinations of iridodysgenesis, trabeculodysgenesis and corneodysgenesis. This paper is concerned with the response to goniotomy in infants with isolated trabeculodysgenesis (Primary congenital or infantile glaucoma). Such cases with signs and symptoms presenting in the first to the twenty-fourth month of life are excellent candidates for goniotomy and have a good prognosis. Those with signs and symptoms at birth or after 24 months should have at least one goniotomy before resorting to trabeculotomy or trabeculectomy. The long-term prognosis of eyes successfully treated by goniotomy is good. However of 50 cases followed for 15 to 25 years with pressures ranging between 10 and 20 mm Hg without medication, 7 (14 per cent) developed complications after 15 years. Three had increases in intraocular pressure; two had retinal detachments and two had mild corneal oedema from endothelial dystrophy. Forty-six per cent had some degree of deprivation amblyopia. Few of these cases are as yet in their thirties. The truly long-term prognosis is as yet unknown. It is of great importance that these patients have periodic eye examinations throughout their life.