During the last two decades, much research has focused on the mechanisms used by nonhuman primates for conflict resolution. Reconciliation, i.e., a friendly reunion between former opponents, has been reported in several primate species. Reconciliation seems to serve at least two functions. According to the Valuable Relationship Hypothesis, reconciliation restores the disturbed relationship between former opponents and, consequently, occurs more often between individuals with more valuable relationships. The Uncertainty-Reduction Hypothesis emphasizes the function of reconciliation to reduce anxiety and uncertainty in the recipient of aggression following a conflict. The study of post-conflict emotionality facilitates the integration of these two hypotheses. The present study focuses on the factors affecting post-conflict anxiety of the two former opponents. Post-conflict data of captive Barbary (Macaca sylvanus) and long-tailed macaques (Macaca fascicularis) are used here to examine patterns of anxiety-related behavior, such as self-scratching. The fact that in the first minutes following a conflict not only recipients of aggression but aggressors too increased the rate of scratching above baseline levels suggests that the risk of renewed attacks is unlikely to be the only reason for post-conflict anxiety. The quality of the relationship between former opponents was a good predictor of post-conflict scratching rates by the recipient of aggression: Rates were higher after conflicts between individuals with stronger affiliative relationships. This result was not due to differential risk of resuming hostilities or arousal resulting from the intensity of the previous conflict. This finding suggests that the disturbance of a valuable relationship due to the previous conflict (e.g., the potential loss of benefits provided by such relationships) is a major cause of post-conflict anxiety. In line with the Uncertainty-Reduction Hypothesis, the best way to cope with post-conflict anxiety is to reconcile and therefore restore the relationship. Higher levels of post-conflict anxiety should lead therefore to higher conciliatory tendency. This interpretation is supported by the fact that individuals with strong affiliative relationships reconcile more frequently than others, as predicted by the Valuable Relationship Hypothesis. The mediating role of emotions, such as post-conflict anxiety, is probably not limited to reconciliation. Other post-conflict interactions, such as consolation, triadic reconciliation, and mediation, are also likely to be better understood if future studies focus on the post-conflict emotions of the opponents and bystanders. Aggr. Behav. 23:315–328, 1997. © 1997 Wiley-Liss, Inc.