In tumors with a loss of MLH1 protein expression, MLH1 promoter methylation was detected in 66.5% (95% CI: 44.4–83.2%) of the 106 total CRC, 80.8% (95% CI: 75.3–85.3%) of the 247 MSI-H CRC, 69.8% (95% CI: 45.5–86.5%) of the 156 sporadic CRC, and 37.8% (95% CI: 25.3–52.1%) of the 169 LS tumors (P<0.001). The gene discussed is MLH1; the disease is colorectal carcinoma.