Six frogs (Rana nigromaculata 25∼40 gm) were adapted to light for 2 hours. Then 0.02 ml of 3% nicotinamide and 0.02 ml of 0.6% folic acid were injected into the vitreous body of the right eye-ball, and 0.02 ml normal saline solution into the vitreous body of the left eye-ball respectively. After dark adaptation for an hour-their heads were cut off under a dim red light (650 $m{mu}$). The retinae were removed from the left eye-ball for the control group and from the right for the test group respectively. Then rhodopsin was extracted from the retinae with 3 ml of 2% digitonin solution(pH = 7.0) for 17 hours at 0$^{circ}C$ in the dark. The optical densities before and after the illumination of the extract were measured and compared with those of the control group. The results are as follows: 1) The group which had been injected with 0.02 ml of 3% nicotinamide solution had the promotive action on tile regeneration of rhodopsin in comparison with the control group. 2) The group which had been injected with 0.02 ml of 0.6% folic acid solution had the controlling action on the regeneration of rhodopsin in comparison with the control group.