Respiratory symptoms were the first manifestation of illness in a 17-year-old boy with a diagnosis of periarteritis nodosa. Over a period of several months he developed pulmonary infiltrates, peripheral eosinophilia, abdominal distress, and mononeuritis multiplex. As the disease became progressively more severe, it no longer responded to increasing doses of prednisone. Azathioprine therapy was started in addition to prednisone and the patient has had clinical remission of symptoms for 11 months.