Eighty clients meeting criteria for panic disorder and receiving either panic control therapy (PCT; M. G. Craske, E. Meadows, & D. H. Barlow, 1994) or treatment as usual (TAU) in a managed care setting were assessed 1 and 2 years following acute treatment. PCT was provided by therapists with little or no previous exposure to cognitive-behavioral therapies. Analyses of the full intent-to-treat sample revealed no significant differences between the treatments across the follow-up period. However, when treatment completer status was added as a moderator, those receiving PCT showed lower levels of panic severity and phobic avoidance and a greater likelihood of achieving and maintaining clinically significant change. Benzodiazepine use during follow-up was associated with greater panic severity for those clients who received PCT, but no such relationship was found for TAU clients. Results are discussed in relation to the dissemination and effectiveness of PCT as well as evidence based psychotherapies more generally.