Organophosphate containing insecticides, especially those widely used in the agricultural field, have harmful effects on human. In this study, our aim was to study the relation among clinical and laboratory findings and the parameters such as amount of organophosphate, serum paraoxanase (PON) and pseudocholinesterase (CHS) concentration and the phenotype of PON, in patients with pesticide intoxication. Forty two patients with organophosphate intoxication (OPI) and 45 healthy volunteers as control were included in this study. Patients were divided into groups according to the severity of their clinical conditions and treated after vital examinations and routine blood tests were done. Serum PON activity, arylesterase activity, PON phenotype determination and acetylcholinesterase activity tests were carried out for both the patient and the control groups. No statistical difference was detected in either group in terms of basal PON values and phenotypes. Acetylcholine values in the patient group were significantly lower. The atropine usage in conscious patients was significantly lower than unconscious patients. A significant difference was detected in the dose of used atropine between the clinically mild and moderate patients and the clinically mild and severe patient groups. The atropine requirement in the patient group needed endotracheal intubation was significantly higher than the patient group who did not require intubation. The average age of the recovered patients were significantly lower than those who died. The dose of organophosphate was lower in the recovered patient group when compaired to died patients. In conclusion, higher atropine requirements is associated with the clinical severity and entubation requirement in organophosphate intoxication. Advanced age is associated with higher mortality. PON phenotype has no relation with clinical condition and various biochemical parameters.