In this issue of the Journal, Cheon and coworkers have examined the utility of serum IL-6 values as a biomarker for cholangiocarcinoma (CCA). Serum IL-6 values were increased in patients with CCA as compared to controls or patients with hepatocellular carcinoma. IL-6 levels also correlated with tumor thickness (a surrogate for tumor burden) as examined by intraductal ultrasonography, a novel approach for assessing CCA tumor burden. Following photodynamic therapy, serum IL-6 values decreased. This study suggests IL-6 may be a biomarker for CCA, confirms the efficacy of photodynamic therapy (PDT) as an antineoplastic therapy, and implies that targeted IL-6 therapy may be beneficial in CCA.