BACKGROUND/AIM Combretastatin A-4 phosphate (CA4P) is a vascular-disrupting agent which affects the level of circulating neutrophils. Since tumor-associated macrophages and neutrophils may collaborate, we compared the effect of CA4P treatment on monocytes/macrophages and neutrophils. MATERIAL AND METHODS CDF1 mice with a C3H mammary carcinoma foot tumor were injected intraperitoneally with CA4P. Blood samples were taken and tumors excised at various time-points after treatment. Circulating monocytes and granulocytes were detected by flow cytometry and the tumor levels of these cell types was estimated immunohistochemically. RESULTS CA4P induced similar oscillating effects on the level of circulating monocytes and of neutrophils, with an initial decrease followed by an increase and a return to control levels at 6-h and 24-h, respectively. In tumors, only the macrophage level decreased significantly after treatment. CONCLUSION CA4P induced similar changes in the level of circulating monocytes and neutrophils, but only affected the fraction of macrophages significantly.