The effect of γ-ray irradiation on polyphosphates in aqueous solution and in "kamaboko" was investigated to evaluate the rate of decomposition and to examine the safety of the decomposed products. Tripolyphosphate, pyrophosphate and o-phosphate in aqueous solution were very stable against γ-ray irradition, respectively. Tripolyphosphate added to "surimi" (minced and washed flesh of Alaska Pollack) completely changed to o-phosphate during the period of processing "kamaboko", but pyrophosphate was remained. Pyrophosphate content in "kamaboko" decreased in proportion to the dose of γ-ray. Decreased pyrophosphate was presumed to change into such products as insolubles which can not be extracted with 6% perchloric acid solution. Both tripolyphosphate and pyrophosphate changed enzymatically to o-phosphate. The activity of exopolyphosphatase in "surimi" was still remained. Polyphosphates added to "surimi" changed completely to o-sphosphate during the frozen storage of "surimi", the application of γ-ray irradiation on "kamaboko" was considered not to induce any injurious substances from polyphosphates.