Thein vitroeffects of five widely employed pesticides (i.e., insecticides: malathion and aldicarb; herbicides: diuron, metolachlor, and glyphosate) on the occurrence of oxidative stress [i.e., increased levels of methemoglobin (METHB) amd decreased levels of induced glutathione (GSH)] in erythrocytes from female Dorset sheep, an animal model with low erythrocyte G‐6‐PD activity. The only statistically significant treatments (p 0.05) occurred with malathion and metolachlor which reduced GSH levels at the highest concentration (i.e., 100 ppm) employed by 59% and 45%, respectively.