Sodium lactate infusion provokes panic attacks in panic disorder patients but not in normal controls. We have previously shown that patients who develop panic disorder during a major depressive episode are similar to panic disorder patients in their rate of panic attacks with lactate. In the present pilot study, nine patients with major depression without panic attacks underwent lactate infusions. These patients differed significantly from panic disorder patients but not from controls in their response to lactate. This argues for the specificity of lactate sensitivity for the phenomenon of panic attacks and gives further evidence for biological differences between panic and depression.