Panic episodes were described as a distinct form of anxiety by Freud almost 100 years ago, and the recent publication of the Diagnostic and Statistical Manual of Mental Disorders, third edition (D.S.M.-III), has provided the basis for the separate diagnostic entity of panic disorder. In this study, we showed the historical review of research and the result of our clinical study of panic disorder in 7 patients. The following results were obtained: 1) Abnormal DSTs were observed in only two of 5 patients. 2) Five of 6 patients showed high concentration of adrenaline and noradrenaline in urine. 3) Anxiety was provoked by caffeine in two of 5 patients. 4) Depression of T-wave was shown in three of 5 patients with orthostatic E.C.G. 5) Sinus tachycardia was gained in one of 3 patients with Holter E.C.G. 6) Abnormal respiratory functions were observed in all two patients with Treadmill. 7) Only one small heart was observed on a chest radiograph. 8) Panic attacks were provoked by sodium lactate infusion in four of 7 patients.