OBJECTIVE: Most research on treatment for panic disorder has involved chronic forms of the illness. To determine the efficacy of early intervention, the authors examined the effects of treatment for patients with panic attacks who were seen in the emergency room, which is the first point of contact with the health delivery system for many persons with panic attacks. METHOD: The subjects were 33 patients with panic attacks seen in two emergency rooms. The presence of panic attacks was confirmed with a modified version of the Structured Clinical Interview for DSM-III-R; approximately 40% of the patients met the DSM-III-R criteria for panic disorder with agoraphobia. The patients were randomly assigned to groups receiving reassurance (N = 16) or exposure instruction (N = 17). Scores on the Fear Questionnaire agoraphobia subscale, Mobility Inventory, and Beck Depression Inventory and the frequency of panic attacks were determined at baseline, 3 months, and 6 months. RESULTS: The subjects who received exposure instruction significantly improved over the 6-month period on depression, avoidance, and panic frequency. The reassurance subjects did not improve on any measure and eventually reported more agoraphobic avoidance. CONCLUSIONS: These results suggest that early intervention with exposure instruction may reduce the long-term consequences of panic attacks. The exposure instruction was of value even though the subjects had relatively low levels of avoidance at the outset of the study.