Background Controlled trials have shownthat psychological interventions designed to encourage graded exercise canfacilitaterecovery fromchronic fatigue syndrome. Aims To identifypredictors of response to psychological treatment forchronic

Declaration of interest None. Financial support fromthe LinburyTrust. Chronic fatigue syndrome (CFS) is associated with muscular and cardiovascular deconditioning (De Lorenzo et al, 1998), circadian desynchrony (Williams et al, 1996), sleep abnormalities (Morriss et al, 1997) and cortisol deficiency (Cleare et al, 1995). It has been proposed that these signs are consequences of disrupted cycles of activity, and that CFS is maintained by illness beliefs that encourage activity avoidance (Wessely et al, 1998). Psychological interventions that encourage exercise are effective treatments for CFS (Sharpe et al, 1996; Deale et al, 1997; Powell et al, 2001). We tested the hypotheses that variables indicative of rigid illness beliefs (duration of untreated illness, membership of a support group advocating exercise avoidance, belief in physical illness), limited emotional resources (concurrent dysphoria, receipt of antidepressant medication, sleep problems), poor social support (living alone or as a lone parent), or probable loss of benefits on recovery, would predict poor response to this kind of treatment.