A mature Brangus bull received the recommended dose of chlorpyrifos and became dull and inappetent 3 days later. Clinical findings included weakness, dehydration, rumen stasis, and rumen distention with fluid and gas. Blood cholinesterase activity was 25% of normal. The bull's condition improved after treatment with pralidoxime, antimicrobials, electrolyte solutions, vitamins, and adsorbents. Five weeks later, the bull had gained weight, the blood cholinesterase activity was 70% of normal, and the results of a semen evaluation indicated he was a satisfactory potential breeder.