The histopathological manifestations in four eyes from two male patients with the oculo-cerebro-renal syndrome of Lowe included a small, discoid, cataractous lens, peculiar capsular and epithelial changes with aberrant formation of collagenous fibrous tissue, polar lenticular changes with anterior vitreous condensation, embryonic anterior chamber angle with anterior displacement of rudimentary ciliary processes, segmental hypoplasia of iris dilator muscle, and Lange's folds with peripheral retinal cystoid changes. Additional findings in one of the cases included bilateral corneal keloids, vitreous organization, hyalinized retinal vessels, and mild gliosis. We suggest that the congenital ocular abnormalities in Lowe's syndrome are related to an as yet unidentified, inherited enzymatic and/or biochemical defect, and that they progress further because of an abnormal aqueous humour environment. The role of aminoaciduria and mucopolysaccharidosis in the pathogenesis of systemic and ocular defects is discussed in the light of recent investigations.