Copeptin and arginine-vasopressin are derived from a common precursor molecule and secreted in equimolar amounts. We investigated copeptin secretion during CCK-4 panic provocation. Copeptin correlated positively with panic symptoms. Copeptin correlated also positively with ACTH and cortisol. Findings suggest a role of copeptin as potential surrogate marker of CCK-4 panic symptoms.