The toxicity of the Thailand and Middle-Asian cobra venoms as well as of their isolated components (neurotoxins, cytotoxins, phospholipases and some others) for cockroach Gromphadorhina portentosa was studied. It was found that, as compared to mammals, cockroaches are more resistant to cobra venoms and their components. At intraabdominal injection the most toxic for cockroaches were cytotoxins (LD501.5-2.3nmol/g). Acidic phospholipase A2CM II is less active (2.85nmol/g), while α-neurotoxins, being the most toxic venom components for mice (LD500.01-0.03nmol/g), are not toxic for cockroaches at doses up to 15nmol/g. © 2002 Elsevier Science Ltd. All rights reserved.