Forty Danish panic disorder patients participating in a placebo controlled study of alprazolam and imipramine (The Cross National Collaborative Panic Study, Phase II) were followed up by a telephone interview three years later, with essentially the same battery of evaluation procedures applied at baseline, end of study, and follow-up. The main finding was that panic disorder is a chronic disorder, but fluctuating in form and severity in the course of time. Twenty-five percent of the patients no longer fulfilled the DSM-III criteria for panic disorder, but had substantial disability due to a variety of symptoms, including panic attacks at infrequent rate, generalized anxiety symptoms, affective symptoms, and phobic avoidance behavior. Nearly three fourths of the patients were under treatment at follow-up. Benzodiazepines were the drugs most often prescribed, usually in combination with supportive psychotherapy. It was concluded that the different types of treatment offered were insufficient. Variables predicting panic disorder or substantial disability at 3-years follow-up were few.