To investigate the mechanism by which noncontingent reexposure to the UCS restores an extinguished fear response in rats, a noncontingent footshock reminder was administered to Sprague-Dawley rats at various intervals after extinction of a fear response. Reexposure to the UCS restored an extinguished fear response if the reminder was administered 7 days after extinction but not immediately or 24 h after extinction. A second experiment showed that in the 7-day condition prolonged exposure to the situational cues following the noncontingent footshock attenuated recovery of fear. Results are discussed in terms of changes in the discriminability of the training and reminder contexts as attributes of stimuli are forgotten.