Comparative study of gonioscopic findings and microscopic sections in two normal and three buphthalmic eyes indicates that hereditary buphthalmia in rabbits may result from malformation of anterior chamber angle structures. Undifferentiated uveal tissue, rather than fibrosis or dense tissue which previous studies have implicated in the pathogenesis of hereditary buphthalmia, was seen in the filtration angle of buphthalmic eyes. These studies link malformation of the filtration angle to decreased outflow facility and under-development of the ciliary body to low aqueous formation.