The nodal stage of colorectal cancer is based on the number of positive nodes.It is inevitably affected by the number of removed lymph nodes,but lymph node ratio can be unaffected.We investigated the value of lymph node ratio in stage Ⅲ colorectal cancer in this study.The clinicopathologic factors and follow-up data of 145 cases of stage Ⅲ colorectal cancer between January 1998 and December 2008 were analyzed retrospectively.The Pearson and Spearman correlation analyses were used to determine the correlation coefficient,the Kaplan-Meier method was used to analyze survival,and the Cox proportional hazard regression model was used for multivariate analysis in forward stepwise regression.We found that lymph node ratio was not correlated with the number of removed lymph nodes(r =-0.154,P = 0.065),but it was positively correlated with the number of positive lymph nodes(r = 0.739,P < 0.001) and N stage(r = 0.695,P < 0.001).Kaplan-Meier survival analysis revealed that tumor configuration,intestinal obstruction,serum carcinoembryonic antigen(CEA) concentration,T stage,N stage,and lymph node ratio were associated with disease-free survival of patients with stage Ⅲ colorectal cancer(P < 0.05).Multivariate analysis showed that serum CEA concentration,T stage,and lymph node ratio were prognostic factors for disease-free survival(P < 0.05),whereas N stage failed to achieve significance(P = 0.664).We confirmed that lymph node ratio was a prognostic factor in stage Ⅲ colorectal cancer and had a better prognostic value than did N stage.