Ratios of COX-2 mRNA expression in tumor/normal colorectal mucosa, normalized with respect to tissue weight, correlated best with the corresponding ratios normalized for B2M (R = 0.952; P < 0.0001), and to a lesser extent with those normalized for GAPDH (R = 0.830; P < 0.0001). The gene discussed is PTGS2; the disease is neoplasm.