The acute stress response is a key regulatory system for the maintenance of homeostatic equilibrium that is activated upon an imminent or ongoing disturbance of the "milieu intérieur". In general, the stress response in bony fish is similar to that of mammals. The recent cloning and characterization of corticotropin-releasing hormone-binding protein (CRH-BP) in carp (Cyprinus carpio L.) reflects the conservation of the CRH signaling system throughout vertebrates. Now, we can start to investigate the processes that are mediated by the factors that make up this system. The stress response is only one of these processes.