Previous studies have shown that territorial Red-Backed Salamanders (Plethodon cinereus) react aggressively toward intruding Eurycea cirrigera. Our study tested the hypotheses that male and female Red-Backed Salamanders have short-term memory of such territorial intrusions. We allowed focal males and females of P. cinereus to establish territories in laboratory chambers and then presented them with a caged E. cirrigera (treatment 1) or a caged surrogate control (treatment 2). When the cages were removed, the focal salamanders were alone for 5 min and then exposed to an intruding conspecific of the opposite sex. Males (but not females) exhibited significantly more time in threat displays toward the conspecifics in treatment 1 (displacement of territorial aggression) than in treatment 2. We infer, then, that at least males have short-term memory of a past “event” of territorial intrusion.