The German cockroach, Blatella germanica, is one of the most important household pest that can cause disease on human. Conventional contact insecticides show less efficacy because it is hard to be contacted or digested by cockroach that lives inside small crevice. Ethyl formate(EF), which is a potential fumigant to control various insect pests such as stored grain insects and quarantine pests, can be penetrated wherever air exist and shows toxicity on respiratory system of insect. In this trials, we've demonstrated practical and commercial scale fumigations of EF on German cockroach. Efficacy of EF was described in terms of concentration × time (CT) product. At practical fumigation, EF gave 100% control of German cockroach nymph and adult when the CT product was 43.2g h m-3. When 600m3 scale warehouse fumigation for 15 hours with 5g m-3 of EF, nymph and adult stage of German cockroach were completely controlled. The ventilation time to reduce EF concentration under TLV(Threshold Limit Value, EF=100ppm) was less than 1 hour. These results show that EF can be applied at warehouse or mill house to control German cockroach effectively.