Once territories become established residents often have a high probability of successfully defending their territories against intruders. This advantage often can be explained by intrinsic qualities (e.g., size, body condition, experience) that make residents superior competitors. In addition, residency status can confer an advantage that is independent of fighting ability. We used a laboratory experiment to examine the effect of residency status on aggressive behavior by adults of the Ozark zigzag salamander (Plethodon angusticlavius), a small terrestrial salamander found under rocks and logs on the forest floor. We controlled for intrinsic effects by testing each individual as both a resident and an intruder in random order. Males and females were tested in same-sex contests in separate experiments. Based on an index that incorporated the frequency of aggressive and submissive postures, both males and females were significantly more aggressive as residents than as intruders. Bites were performed by both males and females, occurring in 11 of 38 pairings overall, and also tended to be more frequent in residents than in intruders (P = 0.057). These data are consistent with the hypothesis that both males and females defend feeding territories and that residency offers an advantage that is independent of fighting ability in this species.