The study was carried out to investigate the neurotoxic and immunotoxic effects of fenthion-and omethoateused agricultural areas on frogs (Rana ridibunda) at acute exposure. The neurotoxic effects of the chemicals were evaluated by measuring the activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Biomarkers selected for immunotoxic monitoring were the activities of adenosine deaminase (ADA) and myeloperoxidase (MPO) in various tissues of frogs exposed to 10 or 20 parts per million (ppm) dosages of fenthion and omethoate for 24, 48, 72 and 96 hours. Results showed that the administrations of chemicals fluctuated AChE and BChE activities in some tissues of frogs treated with both dosages at all the periods. With regard to the immunotoxic effects, MPO activity was increased in almost all the tissues of frogs after 10 and 20 ppm dosages and for 24, 48, 72 and 96 hours exposure of fenthion and omethoate as compared to those of control whereas ADA activity did not change in all the tissues. This may reflect the potential role of these parameters as useful biomarkers for toxicity of fenthion and omethoate.