Recent cardiac studies have suggested that patients with chest pain and angiographically normal coronaries have "microvascular angina" (MVA). In contrast, prior psychiatric studies have shown that some of these patients have panic disorder (PD). We compared the clinical and psychologic characteristics of fifteen patients with MVA and fifteen patients with panic disorder (PD), and examined response to lactate infusion in a subgroup of MVA patients. Although 40 percent of MVA patients met criteria for PD and had chest pain following lactate infusion, there were psychologic and symptomatic differences between the MVA and PD groups. These results reflect either co-morbidity of MVA and PD in some patients or two types of MVA, one of primary cardiac origin and one a centrally mediated epiphenomenon of the increased autonomic arousal seen in PD.