In this pilot study, 9/9 patients with panic disorder experienced a lactate-induced panic attack as compared with 0/9 controls. Baseline measurements were significant for higher anxiety self-ratings, higher heart and respiratory rates, elevated potassium, and lower lymphocyte 3H-dihydroalprenolol (DHA) binding in the patient group. Spielberger State anxiety scores correlated with baseline mean heart rate, and Spielberger Trait anxiety scores with lymphocyte DHA binding. The lactate infusion was not found to differentially affect any physiological or biochemical measures in the two groups, though heart rate surges occurred in most patients. Intravenous propranolol reduced the panic to a negligible degree, whereas intravenous diazepam was quite effective. Neurobiological implications are discussed, and the contradictory biological findings in the lactate literature are reviewed.