Recalling a previously consolidated aversive memory by a reminder?usually a non reinforced re-exposure to the conditioned stimulus (CS)?renders this memory susceptible to disruption again through a variety of amnesic procedures including  Midazolam (MDZ), a benzodiazepine ligandet, The process involved after retrieval is usually referred to as reconsolidation. Our results show that MDZ interferes with the formation of a contextual fear memory only when administered after the reactivation procedure but not after the training procedure. This interference was effective up to 60 min after reactivation and not at a later time. No spontaneous recovery of freezing behavior was observed 11 days after MDZ injection which was not reverted by a weak training trial and by the unconditioned stimulus alone. Over a 10-min reactivation session, all animals gradually reduced theirfear response, which indicates the emergence of the extinction process. When tested, MDZ rats exhibited a robust fear, suggesting that MDZ impaired the consolidation of extinction.  In additin, MDZ?s interference on fear-memory reconsolidation was effective within a relatively short reactivation period in recently acquired memories. Over longer reexposure, MDZ disrupts the consolidation of extinction. A longer duration of the reexposure session, as well as higher MDZ doses, is required to prevent the reconsolidation process of remote fear memories. MDZ did not affect memory reconsolidation inolder-than-one-day memories of stressed animals, even after the administration of a higher MDZ dose.