18 adult male dogs were exposed to 3 treatments: habituation to a hammock, stress induction, and a shuttlebox test. At each stage, blood samples were drawn and plasma cortisol was assayed. In the initial stress-induction phase, the controllability and predictability of electric shocks were independently varied. In a subsequent test phase, all groups received identical shocks in a novel situation. Cortisol responses to these test shocks were analyzed as a function of the controllability and predictability of previous induction shocks. Results show that during stress induction, uncontrollable shocks produced significantly greater cortisol elevations than controllable shocks, but predictability had no significant effect on cortisol responses. However, unpredictable shocks during stress induction acted proactively to significantly increase cortisol responses to novel test shocks, whereas prior controllability did not modulate subsequent responsivity to novel shocks.(54 ref)(PsycINFO Database Record (c) 2016 APA, all rights reserved)