The radioprotective action of mixed tremella preparation（Yinshen Yin） on whole body gamma irradiated dogs has been studied. 25 male dogs were divided into five groups: tremella

mercaminum

Yinshen Yin at high dose

Yinshen Yin at low dose and control. All the dogs were given above drugs in 10 successive days before acute exposure of 1 Gy radiation. The results showed that the prophylaxtic use of Yinshen Yin had good anti- irradiation effect

and the radioprotective effect was similar to the mercaminum

but significantly higher than tremella. Thereby it was considered as a good radioprotective agent. The dose reduction factor in different groups were: Yinshen Yin high dose 2.01

Yinshen Yin low dose group 1.72

mercaminum group 1.55 and tremella group 1.11.