Susceptibility of Periplaneta americana male adults to 61 commercial insecticides was evaluated by diet dipping method. Among them eight insecticides of dichlorvos, benfuracarb, cypermethrin, deltamethrin, fenpropathrin, $zeta$-cypermethrin, $lambda$-cyhalothrin and fipronil showed 100% mortality. The insect was more susceptible to dichlorvos and fenpropathrin in filter paper contact method than in diet dipping one, but benfuracarb was vice versa. Toxicities of the seven chemicals were evaluated by application parts of the such as head, thorax, abdomen, and legs. Dichlorvos, benfuracarb and $lambda$-cyhalothrin were more toxic when applied to head, and deltamethrin, fenpropathrin and cypermethrin were abdomen. $LT_{50}$ values by diet dipping method showed that dichlorvos, benfuracarb and $lambda$-cyhalothrin acted more rapidly than boric acid and hydramethylnon. The values of the former three were 0.10, 0.29 and 0.12 days, and those of the latter two were 6.2 and 4.8 days, respectively.