Our purpose was to determine the incidence of mitral valve prolapse in patients with anxiety neurosis or panic disorder, with symptoms including recurrent anxiety attacks, dyspnea, palpitations, chest pain, dizziness, and paresthesias. Twenty-one patients and 20 age- and sex-matched normal controls were studied. Objective cardiac abnormalities were significantly (p < 0.05) more frequent in the patient group as compared to the control group; these comprised echocardiographic prolapse, ST-T abnormalities on resting ECG, premature ventricular contractions on exercise ECG, and the combination of echo prolapse with clicks/murmurs of exercise-induced PVC. We conclude that patients with anxiety neurosis or panic disorder may also have evidence of an organic abnormality--the mitral prolapse syndrome.