The toxicity of emulsified methylparathion, diazinon, chlorthion and sumicide examined in comparison with that of ethylparathion in laboratory rabbit. The results were as follows. 1) All these compounds were absorbed by means of dermal, oral, subcutaneous snd intravenous application. Methylparathion was 1/21/4, chlorthion was 1/31/8 and sumicide was 1/25 as toxic as ethylparathion, but diazinon was toxic as much the same. 2) These compounds produced a marked depression of cholinesterase (ChE) activities of both serum and red blood cell in all subjects examined. The ChE inactivation caused by methylparathion and sumicide slower than that of the others. 3) The main symptoms caused by exposure to these compounds were alike to those produced by ethylparathion. 4) With the application of these compouuds, the changes of hemoglobin and red blood cell count were not remarkable, except in the sumicide case which the decrease of both occured 2 to 3 days after the administration. There occured, as the case of ethylparathion, leucocytosis, mainly occupied by pseudoeosinophils with the deflection of Arneth count to the left as well as relative lymphocytopenia.