BACKGROUND: This investigation assessed the effect of personality disorders (PersDs) on time to remission in patients with generalized anxiety disorder, social phobia, or panic disorder. METHODS: Selected Axis I and II predictors of time to remission during 5 years of follow-up were assessed in 514 patients with 1 or more of these anxiety disorders who participated in the Harvard/Brown Anxiety Research Program, a multisite, prospective, longitudinal, naturalistic study. RESULTS: The presence of a PersD predicted a 30% lower likelihood of generalized anxiety disorder remission, a 39% lower likelihood of social phobia remission, and no difference in likelihood of panic disorder remission. More specifically, a lower likelihood of remission from generalized anxiety disorder was predicted by the presence of avoidant PersD (34% lower) and dependent PersD (14% lower). The presence of avoidant PersD predicted a 41% lower likelihood of social phobia remission. The presence of major depressive disorder did not account for these findings. CONCLUSIONS: Our findings provide new data on the pernicious effect of PersDs on the course of generalized anxiety disorder and social phobia but not panic disorder, suggesting that PersDs have a differential effect on the outcome of anxiety disorders.