Objective To evaluate the sensitivity and specificity of CA242/CA72‐4 ratio in diagnosing early colorectal carcino‐ma .Methods Totally 87 blood specimens of colorectal carcinoma(CRC) were collected .The Chemiluminescence method was adopt‐ed to detect the levels of CA242 and CA72‐4 .Then the receiver‐operating characteristic (ROC) curve was used to analyze the sensi‐tivity and specificity of CA242/CA72 4 ratio in the diagnosis of CRC .Results Among 87 cases of suspected CRC ,56 cases (64 .37% )were eventually diagnosed as CRC ,31 cases (35 .63% ) were excluded from CRC ;the CA242 and CA72‐4 levels and CA242/CA72‐4 ratios in the CRC group were higher than those in the non‐CRC group ,the differences were statistically significant (P<0 .05) ,moreover the CA242/CA72‐4 ratio was more significant(P=0 .013) .The areas under curve (AUC) of CA242 ,CA72‐4 and CA242/CA72‐4 ratio were 0 .754 ,0 .621 and 0 .775 respectively ,in which CA72‐4 had no significant correlation with the early CRC ,while CA242 and CA242/CA72‐4 ratio had significant correlation with the CRC diagnosis(P=0 .013 ,0 .006) and their 95%confidence intervals (CI) were 0 .576-0 .851 and 0 .612 -0 .887;when the CA242/CA72 4 cutoff value was 2 .6(CA242=28 .6 , CA72‐4=11) ,the sensitivity for early diagnosis of CRC was 91 .32% and the specificity was 94 .57% .Conclusion The sensitivity and specificity of CA242/CA72‐4 ratio in the early diagnosis of CRC are higher than those of CA242 or CA72‐4 single index ,espe‐cially w hen the ratio is close to 2 .6 ,high attention should be paid to the possibility of CRC .