OBJECTIVE: To investigate the correlation between microvessel density (MVD) and expression of vascular endothelial growth factor (VEGF) in tissues of colorectal carcinoma and the micrometastasis of tumor cells in these patients' peripheral blood. METHODS: The MVD and expression of VEGF were evaluated immunohistochemically while the micrometastasis of tumor cells in these patients' peripheral blood was detected by RT-PCR method. RESULTS: The average count of MVD in high and middle differentiation grade was 30.2 +/- 12.7, while in low differentiation grade 86.6 +/- 19.1. The expression of VEGF was positive in 26 patients (44.8%). The MVD and positive expression of VEGF were correlated to differentiations. stage and metastasis of colorectal carcinoma. CK(20) mRNA was found in peripheral blood of 32 patients (55.2%) and the positive rate was up to 60.4% 48 hours after operation, among which positive rate in the radical resection group was 47.7% and in the non-radical resection group 85.7%. 11 out of 21 patients positive in CK(20) mRNA turned to negative 7-14 d after radical resection, while 11 out of 12 patients remained positive at the same time after non-radical resection. The expression of CK(20) mRNA was correlated to the stage and metastasis of the cancer. The MVD and positive expression of VEGF were higher in patients with positive expression of CK(20) mRNA. CONCLUSIONS: The MVD and positive expression of VEGF were correlated to differentiation, stage and metastasis of colorectal carcinoma. The angiogenesis in tissues of colorectal carcinoma was closely related to the micrometastasis of tumor cells in these patients' peripheral blood. The detecting of CK(20)mRNA by RT-PCR may be a sensitive method for evaluating the micrometastasis colorectal carcinoma in peripheral blood and help in prognosis prediction, effect assessment and guidance of multipurpose therapy.