We studied a clinical significance of direct invasion to adjacent organs in Stage IV colorectal cancer. The subjects were 19 consecutive patients who underwent R0 surgery to the primary tumor for colorectal carcinoma, pT4, M1 1995-2003. We studied the relationship of pathologic invasion to adjacent organs of tumor among other clinicopathological factors to prognosis. Of the 19 patients, 11 (57.8%) had R0 surgery to the metastatic tumor. Only 4 (36.7%) patients survived more than 3 years. Of the 8 patients without the surgery, none of the patients survived more than 3 years. And the median survival time was only 8.5 months. Multivariate analysis indicated that RO surgery to the metastatic tumor was only an independent prognostic factor. The optimum resection for adjacent organs may prolong survival. But an extended resection is a possibility in shortening survival time.