Objective: This study compares diagnostic and symptom course trajectories across different anxiety disorders, and examines the role of anxiety arousal vs. avoidance behaviour symptoms in course prediction. Method: Data were from 834 subjects with a current anxiety disorder from the Netherlands Study of Depression and Anxiety (NESDA) who were re-interviewed after 2 years. DSM-IV-based diagnostic interviews and Life Chart Interviews (LCI) were used to assess the diagnostic and symptom course trajectory over 2 years. Anxiety arousal and avoidance behaviour symptoms were measured with LCI, Beck Anxiety Inventory and Fear Questionnaire. Results: Prognosis varied across disorders, with favourable remittance rates of 72.5% for panic disorder without agoraphobia and 69.7% for generalized anxiety disorder; gradually declining to 53.5% for social phobia and 52.7% for panic disorder with agoraphobia. Only 42.9% of those with multiple anxiety disorder remitted, and this group showed a more chronic course than pure anxiety disorders. Both baseline duration and severity were course predictors. Avoidance behaviour symptoms predicted the outcome better than anxiety arousal symptoms. Conclusions: These data suggest that the specific anxiety disorders such as recognized by DSM-IV are useful in predicting the outcome and that this may be determined largely by the relative severity of avoidance behaviour that patients have developed. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.