There has been considerable speculation about a possible relationship between panic disorder and mitral valve prolapse syndrome (MVP), although empirical results have been highly inconsistent. Some studies report low frequencies of 0–8%, others high frequencies of 24–35% “definite” MVP in panic patients (average across 17 studies: 18% of panic patients, 1% of normal controls). Elevated prevalences of MVP were also reported for generalized anxiety disorder, bipolar affective disorder, and anorexia nervosa. Studies of MVP patients generally failed to find elevated prevalence of panic compared to other cardiac patients or normal controls (averages across seven studies: 14%, 10%, and 8%, respectively). Inconsistent results may be due to widely different diagnostic criteria for MVP, low reliability of this diagnosis, inadequate control groups, “non-blind” ratings of panic or MVP, and sampling bias in both patient and control populations. These problems as well as the great variations in the published results preclude any final judgment. If there is concomitance between MVP and panic, it is small and primarily involves subjects with milder or reversible variants of MVP. At present it seems most justified, however, to assume co-morbidity in highly symptomatic individuals rather than a functional relationship.