A hybrid efficacy-effectiveness design in which participants (n = 91/93) were retained in the study regardless of whether or not they received treatment enabled evaluation of CBT intensity in relation to panic disorder in the primary care setting. CBT intensity was operationalized as number of cognitive-behavioral therapy sessions, number of follow-up booster phone calls, and secondarily, as number of cognitive behavioral coping and exposure strategies. Baseline psychosocial and demographic predictors of CBT intensity were analyzed first. Severity of anxiety sensitivity predicted number of cognitive behavioral sessions, but no baseline variables predicted number of follow-up booster phone calls or number of coping and exposure strategies. Multivariate logistic and linear regressions were used to evaluate the degree to which treatment intensity predicted 3-month and 12-month outcomes (anxiety sensitivity, phobic avoidance, depressive symptoms, disability, and medical and mental health functioning) after controlling for potential confounding baseline variables. Number of cognitive behavioral therapy sessions predicted lower anxiety sensitivity at 3 and 12 months, and number of follow-up booster phone calls predicted lower anxiety sensitivity, less phobic avoidance, and less depression at 12 months. These findings indicate that "dose" of psychotherapy was an important predictor of outcome. The significance of follow-up booster phone contact is discussed as an index of continued self-management of panic and anxiety following acute treatment.