Shocks which cannot be controlled by an organism have been shown to interfere with subsequent escape-avoidance training more than do equivalent shocks which can be controlled. 2 experiments extended the generality of this phenomenon by examining the effects of the escapability of shock on subsequent shock-elicited aggression. Exp. I (with 48 male Sprague-Dawley rats) found that prior exposure to inescapable shock reduced the frequency of shock-induced fighting, while escapable shock did not produce such a reduction. The theory that yoked-control procedures can capitalize on individual differences and produce a systematic difference between groups was ruled out as an explanation of the data of Exp. I by the results of Exp. II, conducted with 22 similar Ss. (19 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)