A case of polyarteritis nodosa presenting in the emergency department as grand mal seizures is reported. Seizure as a presenting feature of polyarteritis nodosa is unusual. The nature of the patient's signs and symptoms led to the diagnosis of polyarteritis nodosa, which was supported by arteriography. Therapy with high-dose corticosteroids and cyclophosphamide resulted in rapid improvement. Standard anticonvulsant therapy proved efficacious during the initial treatment of the patient's seizures. The patient died three months later at another facility. Cause of death as determined at autopsy was polyarteritis nodosa. © 1983 American College of Emergency Physicians.