M-CBT produced significantly lower relapse rates (5.2%) and reduced work and social impairment compared to the assessment only condition (18.4%) at a 21-month follow-up. Multivariate Cox proportional hazards models showed that residual symptoms of agoraphobia at the end of acute-phase treatment were independently predictive of time to relapse during 21-month follow-up (hazards ratio = 1.15, p<.01).