This study was carried out to obtain the basic data for the preverition of chronic poisonig by organic phosphate pesticides. 6 sprayers who participated in the summer pest control programs of Jeonju city were chosen as the subjects in this study. Pesticides which were spread in the period of study are DDVP (1.09%), dursban (1.8%) and dibrom (1.9%). And from May 16, 1983 to Aug. 22, 1983, plasma cholinesterase activity, hematological and biochemical parameters were measured with several physical examinations for each sprayers and controls. Major findings are as following; 1. Before pesticides were sprayed, plasma cholinesterase were $7.32{pm}1.76{mu}M/20{mu}l/hr$. in sprayers and $7.13{pm}1.39{mu}M/20{mu}l/hr$. in the control group (p>0.05). 2. At 60th day of spraying, plasma cholinesterase activity of sprayers was $6.78{pm}2.01{mu}M/20{mu}l/hr$. which is significantly decreased from the pre-exposed value (p<0.01), but plasma cholinesterease activity in the control group was not changed. 3. The specific findings which suggested to organophosphorous poisoning were not found through the period of study. 4. Hematological and bichemical parameters were not sigricantly changed in the both groups.