With the purpose to elucidate the influence of parathion exposure on the human body while spraying it in the rice field, the author studied 37 farmers in the Bizen rice-producing farmland as the subjects; and obtained the following results. 1. There is no difference between the physical findings before sparying and those after the spraying. 2. As for subjective symptoms 4 cases (10.8%) complained of the symptoms that can be thought relatively charateristic to parathion poisoning, and 12 cases (32.4%) complained of symptoms that are not characteristic. However., judging them in conjunction with the values of serum cholinesterase, these symptoms are not due to poisoning but they are due to fatigue or incidental ones. In any event, the total of 16 cases (43.2%) had complained about some symptoms on account of spraying parathion. 3. Twenty-four cases (14.8) showed urine p-nitrophenol which is the evidence of absorbing parathion into the body. As those who absorbed parathion at early stage of the spray may no longer show p-nitorphenol in the urine, if these possible cases are added, the actual number of absorbing parathion will be greater. 4. What is a convincing evidence of parathion invasion into the body, namely, inhibiton of serum cholinesterase, can be recognized in 15 cases (40.5%). The ones that showed the greatest reduction of serum cholinesterase as low as minus 64.8 per cent are thought to be on the verge of onset of poisoning. 5. Those who showed either p-nitrophenol in the urine or inhibition of serum cholinesterase, in cther words, those who were really exposed to danger during parathion spraying amounted actually as much as 30 cases, 81 per cent of the total studied. Therefore, at the present method of spraying those actually attacked dy parathion poisoning are rare, but as they are really exposed to that danger, it is desirable to take all possible precautionary measures during the work.