Kamaboko is one of very popular foods in Japan. It is made by cooking the fish muscle pulp well mixed with salt, starch and tasteful ingredients, such as sodium glutamate and sugar or saccharine. It is a serious problem from the hygienic as well as producer's stand point that the kamaboko is readily spoiled and usually possesses only one- or two-day storage life at room temperature. The present study deals with the application of preservatives, casing and various radiations in order to increase the keeping quality of this food. The results obtained can be summarized as follows : 1. Among preservatives which were applied on the surface, hydrogen peroxide, oleic acid having high peroxide value and quaternary ammonium compounds were effective in prolonging the storage life to two to three days in contrast to one day in the control. (See Tables 1-4). 2. The casing with cellophane was found effective to elimination of the secondary contamination. The combination of the casing an,d smearing of preservatives on the surface was effective only when hot surface of the kamaboko was treated with solutions of preservatives followed by casing after few minutes' standing, while a group in which the casing was made just after the treatment with preservatives was rather inferior to the control group without casing. (See Table 5). 3. When the surface was irradiated with infrared ray, the storage life was prolonged to two d ys in contrast to one day in the control. It was observed that micro-organisms were not developed on the upper surface but only on the side. The application of hydrogen peroxide followed by the irradiation was slightly more effective than irradiation only. (See Table 6). 4. Irradiation by infrared ray on the surface of a cellophane-covered kamaboko gave no improvement as compared with cellophane covered control without irradiation. No improved results in this case was observed due to the application of preservatives before casing with cellophane. Daily irradiation, however, resulted in a marked prolongation of the storage life. (See Table 7). 5. Daily irradiation by ultraviolet ray on the surface of the kamaboko without casing was effective to prolonging the storage life as long as four days in contrast to one day in the control group without the irradiation. No effect of keeping quality was obtained due to the application of preservatives. (See Table 8). 6. Daily irradiation on the surface of the cellophane-covered kamaboko by ultraviolet ray was effective to prolongation of the storage life to two days as contrasted to one day without irradiation. Among preservatives applied on the surface before casing and irradiation, hydrogen peroxide was found the most effective. (See Table 9). 7. Daily irradiation by ultraviolet ray all over the surface of the kamaboko which was covered with cellophane after few minutes following the smearing of preservatives on hot surface was effective to prolongation of the storage life to three days in contrast to two days in the control without irradiation of ultraviolet ray. Among the preservatives applied, hydrogen peroxide and butyl p-oxybenzoate were more effective than any other one under test. (See Table 9). 8. Daily irradiation on the surface of the kamaboko without casing by infrared ray followed by ultraviolet ray was able to make the storage life four days as contrasted to one day in the control group without irradiation. The combination of this procedure with preservatives gave no improvement. (SeeTable 10). 9. Daily irradiation of infrared and ultraviolet ray on the surface of the cellophane-covered kamaboko was able to prolong the storage life to three days in contrast to two days in the covered control without irradiation. When the casing was made just after the application of the preservatives, no better effect was resulted. (See Table 11). 10. However, when infrared ray was irradiated before the application of the preservatives, somewhat effective result was obtained ; particularly the application of butyl p-oxybenzoate and hydrogen peroxide mixed with maleic acid were found to keep the quality for four days. (See Table 11).