For the purpose of preventing invasion of Trimeresurus flavoviridis, Habu, the venomous snake, the effect of an electric fence made of hollow tile blocks or polyethylene net was examined in 3 villages on Amamioshima and Tokunoshima islands in the southernmost area of Japan. The electric pulses were supplied by a pulse maker at 0.75 sec. intervals with 480 mA, 0.13 m coulombs at a load of 500 ohms and estimated peak of 8 to 10 kV. The anode from a pulse maker was connected to a stainless steel plate or a metal string woven in a vinyl rope on the fence and the cathode was grounded. The power to the pulse maker was generated by silicon solar cells, stored in a car battery and regulated by an electric eye switch to activate it at night. The necessary height of the fence to prevent Habu from slithering over the fence was experimentally determined to be 60 cm. In 3 villages, 6.75 ha were enclosed with 1000 m fence, 13.7 ha with 2100 m and 23.8 ha with 2500 m, respectively. The effect of the electric fence was remarkable as determined by the annual monitoring of the number of snakes sighted by people and the captivity rate in box traps inside the fence. The number of snakes found annually in Tean Village was 10 before construction and 5, 4, 5 after construction; 119 before construction 55, 20, 20 after construction at Tete; and 109 and 82 before construction and 15 and 11 after construction at Todoroki. The snakes were observed to aggregate outside the fence. The net barrier could be constructed at any topographical conditions with less expense. The effect was further pronounced when snakes were removed by box trap and other methods from inside the fenced area.