A meta-analysis of the efficacy of cognitive behavioral therapy (CBT) in treating chronic fatigue included 15 effect sizes for between-group outcome comparisons. Across analyses, which included a total of 1371 participants, there was a significant difference, d=0.48, in post-treatment fatigue between participants receiving CBT and those in control conditions. Results indicate that CBT for chronic fatigue syndrome tends to be moderately efficacious. Dropout rates in CBT varied from 0-42%, with a mean of 16%. In the five studies that reported the number of CBT clients who were no longer in the clinical range with regard to fatigue at the latest follow-up, the percentage varied from 33% to 73% of those assigned to CBT, with a mean of 50%. Moderator results suggest directions for future investigations.