In the present paper enzymatic properties of the trypsins from the four dark fleshed fish were compared with each other and thermal stabilities of the enzymes were also investigated. The trypsins from the dark fleshed fish showed their activity only in BA-p-NA substrate of the amide substrates such as BA-p-NA and SP-p-NA, and BAEE and TAME of the ester substrate such as ATEE, BAEE, BTEE, and TAME. The enzymes were strongly inhibited by the serine protease inhibitors such as antipain, leupeptin, TLCK, DFP and SBTI, and were also inhibited by such metal ions as Cu$^{2＋}$ and Hg$^{2＋}$, but fairly activated by $Mg^{2＋}$. Denaturation constants of the enzymes were 13.4$ imes$10$^{-4}$ sec$^{-1}$ for anchovy trypsin, 47.18$ imes$10$^{-4}$ sec$^{-1}$ for mackerel trypsin A, 34.06$ imes$10$^{-4}$ sec$^{-1}$ mackerel trypsin B, 42.28$ imes$10$^{-4}$ sec$^{-1}$ for yellowfin tuna trypsin and 16.6$ imes$10$^{-4}$ sec$^{-1}$ for albacore trypsin at 55$^{circ}C$. The activation energies of the trypsins at a temperature range of 3$0^{circ}C$ to 5$0^{circ}C$ were estimated to be 13.91 ㎉/mole for anchovy trypsin, 11.61㎉/mo1e and 8.43㎉/mole for mackerel trypsin A and for mackerel typsin B, 4.35㎉/mole for yellowfin tuna trypsin, and 3.76㎉/mole for albacore trypsin.