Because cancer samples are an admixture of many different cell types, and there were conflicting reports of ABCB1 predictive value depending on whether studies were done at the mRNA or protein level (Vergier et al., 1993), we performed an immunohistochemistry (IHC) study of ABCB1 expression in a large cohort of chemo-naïve prostate cancer tissue samples. The gene discussed is ABCB1; the disease is prostate carcinoma.