A premature infant who was developing cicatricial retrolental fibroplasia, was given cryotherapy to both eyes. This stopped the progress of the disease in almost all areas of the retina. The infant died three months later of complications related to prematurity. A comparison between the inadequately treated areas and those adequately treated during the clinical follow-up prior to death and in the pathology of the eyes confirms the value of cryotherapy in preventing cicatricial retrolental fibroplasia and indicates where it should be applied.