Panic disorder, which is found in about 1.5 percent of the population at some time in their lives, includes recurrent episodes of sudden, unpredictable, intense fear accompanied by symptoms such as palpitations, chest pain, and faintness. Panic attacks, which do not meet these diagnostic criteria fully, are two to three times more prevalent. Since panic symptoms can mimic those of other medical disorders, patients with these symptoms use medical services frequently. To determine the risk of suicidal ideation and suicide attempts in panic disorder and attacks, we studied a random sample of 18,011 adults drawn from five U.S. communities. Subjects who had panic disorder, as compared with other psychiatric disorders, had more suicidal ideation and suicide attempts, with an adjusted odds ratio for suicide attempts of 2.62 (95 percent confidence interval, 1.83 to 3.74). The odds ratio was 17.99 (95 percent confidence interval, 12.18 to 26.58) when the group with panic disorder was compared with subjects who had no psychiatric disorder. Twenty percent of the subjects with panic disorder and 12 percent of those with panic attacks had made suicide attempts. These results could not be explained by the coexistence of major depression or of alcohol or drug abuse. We conclude that panic disorder and attacks are associated with an increased risk of suicidal ideation and suicide attempts. Physicians working in general medical settings and emergency departments should be alert to this problem.