Rats were submitted to a training and a test session of shuttle avoidance. Exposure to a session of extinction of this task either 2 or 24 h after training interfered with retention test performance. Exposure to an open field 2, but not 24 h after the avoidance training also interfered with retention. Diazepam blocked the deleterious effect of extinction and of the open field on retention of the avoidance task. Diazepam alone had no effect when given after avoidance training; it did, however, also interfere with retention when given prior to training. It is likely, therefore, that diazepam cancelled the effect of the extinction or of the open field on avoidance retention because of anterograde amnesia (i.e., it prevented the recording of these tasks). The deleterious effect of the open field on retention of shuttle avoidance can be explained by retroactive interference caused by the addition of information. It is not due to a direct influence on retrieval, it is not due to extinction, and it had to be recorded 2 h after training in order to the effective.