A 3-year-old German Short-haired Pointer was examined because of extreme agitation, hyperactivity, and vomiting that began within 24 hours after ingestion of approximately 750 mg of pemoline, a CNS stimulant. On physical examination, the dog was agitated, tachycardic, hyper-responsive, pyrectic, disoriented, and had mydriasis. These signs were consistent with excessive stimulation of the CNS and sympathomimetic effects resulting from pemoline toxicosis. Serial blood and urine samples were obtained, and toxicologic analyses were performed. Extrapolation of the plasma pemoline concentration 32 hours after ingestion provided an estimated peak plasma concentration of 368 micrograms/ml, dramatically higher than a therapeutic concentration of 1.7 to 7.0 micrograms/ml reported for children. Several sedatives were administered intravenously to alleviate clinical signs and to allow administration of activated charcoal (PO) and fluids (IV). Clinical signs resolved approximately 72 hours after ingestion of pemoline.