Effects of elimination of the opportunity to escape and pretreatment with 3 mg/kg of d-amphetamine were separately examined in rats which exhibited relatively poor performance in a discriminated avoidance-escape situation. Removal of escape opportunity led to marked deterioration in avoidance performance, which could be reversed by reinstatement of the escape contingency. Administration of d-amphetamine brought about a significant improvement in avoidance performance without affecting lever responding in non-CS periods. D-amphetamine was also found not to affect responding to exteroceptive stimuli that had not previously been correlated with shock. An interpretation which emphasizes breakup of CS-induced freezing patterns by d-amphetamine appears the most logical of several possible explanations for the drug's effects. (PsycINFO Database Record (c) 2006 APA, all rights reserved)