['Stress management interventions reduce distress symptoms and hypothalamic-pituitary-adrenal (HPA) axis hormones such as cortisol, which has been related to a down-regulation of immune system components relevant to the human immunodeficiency virus (HIV) infection. We previously showed that HIV+ men assigned to a 10-week cognitive behavioral stress management (CBSM) intervention showed more CD4+CD45RA+CD29+ lymphocytes, an indicator of immune system reconstitution, at a 6- to 12-month follow-up compared with controls. Here, we tested whether reductions in urinary cortisol output and depressed mood during the 10-week CBSM intervention period mediated its effects on this immune system reconstitution marker at follow-up.', 'Twenty-five HIV-infected men randomized to either a 10-week CBSM intervention or a wait-list control provided 24-h urine samples and psychological responses pre- to postintervention, which were related to changes in immune status over a 6- to 12-month follow-up period.', 'Greater reductions in cortisol output and depressed mood during CBSM appeared to mediate the effects of this intervention on this indicator of immune system reconstitution over the 6- to 12-month follow-up period. Changes in mood were maintained over the follow-up period, although these did not add explanatory information beyond the cortisol and mood changes that were observed during the 10-week intervention period. These findings were not explained by the changes in medications or health behaviors during follow-up.'] Are increases in a marker of immune system reconstitution predated by decreases in 24-h urinary cortisol output and depressed mood during a 10-week stress management intervention in symptomatic HIV-infected men?