Chronic graft-versus-host disease (cGVHD) remains a major cause of non-relapse morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Currently there are no accepted measures of cGVHD activity to aid in clinical management and disease staging. We analyzed clinical markers of inflammation in the sera of patients with established cGVHD and correlated those with definitions of disease activity. In all, 189 adults with cGVHD (33% moderate and 66% severe according to National Institutes of Health (NIH) global scoring) were consecutively enrolled onto a cross-sectional prospective cGVHD natural history study. At the time of evaluation, 80% were receiving systemic immunosuppression and failed a median of four prior systemic therapies (PST) for their cGVHD. Lower albumin (P<0.0001), higher C-reactive protein (P = 0.043), higher platelets (P = 0.030) and higher number of PST (P<0.0001) were associated with active disease defined as clinician's intention to intensify or alter systemic therapy due to the lack of response. Higher platelet count (P = 0.021) and higher number of PST (P<0.0001) were associated with more severe diseased defined by NIH global score. This study identified common laboratory indicators of inflammation that can serve as markers of cGVHD activity and severity.