Nettleship1in 1907 was the first to indicate the extent of retinitis pigmentosa in the population when he reviewed the records of 100 patients whom he had personally observed and of 1,600 other patients concerning whom he was able to secure adequate descriptions. He noted other disturbances associated with retinitis pigmentosa but particularly emphasized "degenerative" disturbances of the central nervous system associated with congenital somatic defects. Males predominated in his group (61 per cent), in Cockayne's2(61 per cent), in Bell's3(55.6 per cent) and in ours (61 per cent). We have studied forty-one patients with retinitis pigmentosa and found that the retinas were clearly involved in each of them. Thinning of the retinal vessels was common, with deposits of black pigment usually in the periphery and following the vessels. At times it covered the central part of the retina. Often it was of the "spider-web" configuration, in some patients it took the form of linear streaks, in others it