Nineteen BALB/c, 14CBA/KI, 12C3H/HeJ and 15 (CBA/Kl x C3H/HeJ) F1 female mice were irradiated with 850 rad gamma-rays and transferred with 10(7) syngeneic bone marrow cells 24 hrs later. The occurrence of cataract was examined in these animals. All the BALB/c mice showed visible lens opacification in both eyes between 113 and 149 days after irradiation. All the animals were autopsied 6 months after irradiation and examined for opacification of their lenses. The proportion of opaque lenses was 100, 7.1, 16.7 and 0% in BALB/c, CBA/Kl, C3H/HeJ and (CBA/Kl x C3H/HeJ) F1 mice, respectively. The results indicate that BALB/c mice are much more sensitive to radiation-induced cataractogenesis than CBA and C3H mice.