Consolidation refers to item stabilization in long-term memory. Retrieval renders a consolidated memory sensitive, and a "reconsolidation" process has been hypothesized to keep the original memory persistent. Some authors could not detect this phenomenon. Here we show that retrieved contextual fear memory is vulnerable to amnesic treatments and that the amygdala is critically involved. Cholinergic and histaminergic systems seem to modulate only consolidation, whereas cannabinoids are involved in both consolidation and reactivation. The lability of retrieved memory affords opportunities to treat disorders such as phobias, post-traumatic stress, or chronic pain, and these results help searching for appropriate therapeutic targets.