By using anti-NHK-ras and K-ras monoclonal antibodies, paraffin-embedded tissue specimens of 70 cases of colorectal cancers were immunohistologically examined. Correlation between incidence of expression of these oncogenes and either of postoperative survival rate and stage of colorectal cancer were calculated. The positive rate of anti-NHK-ras and K-ras staining were correlated with maximum diameters of tumor, staging, degree of Dukes classification and depth of invasion. Positive and negative rates of between NHK-ras and K-ras staining were well coincident. The cumulative postoperative survival rate of negative cases for anti-K-ras staining showed a significantly higher survival rate than that of the positive cases.