Commentary on Cochrane corner. Chronic fatigue syndrome (CFS) is syndrome of unremitting fatigue of at least 6 months’ duration that causes significant disability. Exercise therapy has a proven track record in medicine and could be effective for some patients with CFS. An updated Cochrane review of eight studies appeared to suggest that exercise helps fatigue symptoms, but with only a small probability of recovery and/or improvement in daily function. Provisional data on acceptability suggest that most patients are willing to participate. However, one key study (PACE), which was well powered and influential in the Cochrane review, has been met with considerable controversy owing to lack of clarity on outcomes. Following release of the PACE study primary data, re-analysis suggested smaller effect sizes than initially reported. Login using your SSSFT NHS OpenAthens for full text. SSOTP - You can request a copy of this article by replying to this email. Please ensure you are clear which article you are requesting.