The present invention relates to synergistic combinations of the compound 5, 6-dimethylxanthenone-4-acetic acid (DMXAA) and a compound selected from anthracyclines and topisomerase II inhibitors, which have anti-tumor activity. Preferably, the present invention relates to synergistic combinations of the compound 5,6-dimethylxanthenone-4-acetic acid (DMXAA) and a compound selected from etoposide, and doxorubicin. More particularly, the invention is concerned with the use of such combinations in the treatment of cancer and pharmaceutical compositions containing such combinations. The invention further provides for methods of preparing the combinations of the invention.