Tumor angiogenesis has been shown to be associated with metastatic potentials in breast, lung and prostatic carcinomas. The relation between tumor angiogenesis and metastatic potentials in colorectal cancer has not been established to date. We analysed 66 selected patients with colorectal carcinomas (37 with and 29 without nodal metastases) for the microvessel density, tumor proliferation activity, and the clinicopathologic parameters including size, stage, histologic grade, growth pattern, presence of angioinvasion, perineural invasion and lymph node metastasis. For evaluation of microvessel density and tumor proliferative activity, the primary tumors were immunohistochemically stained for CD31 and PCNA. The mean microvessel counts (MVC) per 200X field were 99.27+/-23.28 and 131.35+/-31.48 in node-negative and node-positive patients, respectively. The PCNA index was 39.41+/-5.63% and 56.60+/-7.09% in node-negative and node-positive patients, respectively. MVC and PCNA index were higher in tumors with nodal metastasis (p=0.002, p<0.001), and also correlated each other (sr=0.33, p=0.007). Higher microvessel counts were seen in tumors with advanced stage (p=0.016). Tumor proliferation activity assessed by PCNA immunostaining was significantly higher in tumors with advanced stage, perineural invasion, angioinvasion, poor differentiation and larger size. From these results, MVC and PCNA index in colorectal carcinomas are assumed to be valuable prognostic parameters. Thus assessment of tumor angiogenesis and tumor cell proliferation in colorectal carcinomas may be helpful for the patients in need of aggressive therapy.