Ten cases of cataract which seem to have been caused by exposure to the atom bomb blasts at Hiroshima and Nagasaki are descr. Of the 10 subjects, 7 were males and 3 females, ages at time of exposure varied from 13 to 55 yrs., all were within 550-950 m. of the hypocenter of the explosion, all were in the open or shielded by wooden structures at time of explosion, all had epilation of the head after a latent period of 1-4 wks. with complete baldness lasting 3-7 mos., and all had normal vision at time of explosion. The only ocular complaint of the subjects was failing vision, latent period varying from 6 to 30 mos. The cataracts consisted of opacities in the axial zone of the posterior lenticular capsules over an area of 2-4 sq. mm., with occasional punctate dots farther toward the periphery; the findings were approx. symmetrical in the 2 eyes. Detailed nature of the cataracts is descr.