Purification and biochemical experiments on the carboxylesterases-III (CE-III) from the indian meal moth, Plodia interpunctella (Hubner) were carried out to understand their enzymemological characteristics. The CE-III from the fifth instar larvae was purified by means of ammonium sulfate fractionation, gel permeation choromatography and ion exchange choromatography. The optimal temperature for the reaction of the CE-III on the 4 substrates ($alpha$-Na, $alpha$-Nb, $eta$-Na and $eta$-Nb) was confirmed at 4$0^{circ}C$. The optimal pH for the reactions on the substrates $alpha$-Na and $alpha$-Nb was 7.5. But the optimal pH on the substrate $eta$-Na and $eta$-Nb was 8.0. The optimal substrate concentration for the reactions of the CE-III was 3.16 X 10$^{-3}$ M in $alpha$-Na and $eta$-Nb. On the substrate $eta$-Na and $alpha$-Nb, the optimal substrate concentration was 1.0 X 10$^{-3}$ M for CE-III. The $V_{max}$ and $K_{m}$ values of the carboxylesterases were varied by the substrates as followings: the $V_{max}$ of CE-III was 45.9 for $alpha$-Na, 52.6 for $eta$-Na, 36.4 for $alpha$-Nb, and 83.3 ($mu$ mol/min/mg protein) for $eta$-Nb. The $K_{m}$ of CE-III was 1.43 X 10$^{-4}$ M for $alpha$-Na, 3.57 x 10$^{-5}$ M for $eta$-Na, 9.17 X 10$^{-5}$ M for $alpha$-Nb, and 7.14 X 10$^{-5}$ M for $eta$ -Nb, respectively. The CE-III seemed to have somewhat high thermostability considering that the temperature for effective denaturation on activity was about 5$0^{circ}C$ ～ 6$0^{circ}C$.EX>.EX>.