Abstract: Objective To investigate the effects of different doses of bevacizumab on irinotecan distribution in nude mice bearing human colon cancer cell xenografts. Methods DLD-1 human colon cancer cells were inoculated into 24 nude mice, which were randomly divided into four groups: control group, with 0.9% NaCl on d1, 5, 9 and irinotecan on d10; test group 1 to 3, with bevacizumab 2.5, 5 and 10 mg/kg respectively on d1, 5, 9 and irinotecan on d10. Tumor volume and irinotecan concentration in peripheral blood and xenograft tumor tissues in the four groups after treatment were analyzed. Results No significant difference in tumor volume was observed among groups. Irinotecan concentration in peripheral blood in the three test groups was significantly higher than that in the control group, and increased in a dose-dependent manner(432.33±104.76), (409.69±267.15) and (719.21±253.00) vs. (299.69±83.63)ng/ml, moreover, there were significant difference between test group 3 and test group 2, control group (P=0.045, 0.010). Irinotecan concentrations in tumor tissues from the test groups were lower than that in the control group, and there was significant difference between test group 3 and control group (P=0.047). Conclusion Bevacizumab might influence irinotecan distribution in nude mice bearing colon cancer cells in a dose-dependent manner.