Variations in the calcium content of human lenses undergoing cataractous changes require further study for two reasons : (1) the association of cataract with hypoparathyroidism, a pathologic state resulting from insufficiency or absence of the glands which presumably regulate calcium metabolism, discussed extensively by Fischer and Triebenstein,1 Kerr, Hasford and Shepardson,2 Eiseman and Luckhardt,3 Lenhard,4 Kirby,5 O'Brien6 Evans and Kern,7 and (2) the increase of calcium in cataractous lenses, shown by chemical analyses by Burge,8 Adams,9 Updegraff10 and myself11 and the joint work of Mackay, Stewart and Robertson.12 According to these investigators the calcium content of cataractous lenses is extremely variable. In a previous publication I 11 pointed out that incipient cataracts contain little or no calcium ; however, only slight attention was paid at that time to the exact stage of maturity or to the slit-lamp examinations