This study is to investigate the synergistic effect of Anglica polysaccharide sulfate (APS-1) and Combivir, an anti-AIDS drug, on murine leukemia virus in vivo. As the results shown, the virus replication was significantly decreased by the combination of APS-1 and Combivir, which tended to be further decreased (58% inhibition) when compared with that of Combivir alone (51% inhibition). Furthermore, both the percentage of CD4(+) cells and CD4(+)/CD8(+) ratio in peripheral blood cells were significantly enhanced by this combined administration, while the CD4(+) cells was only slightly increased and CD4(+)/CD8(+) ratio was not affected by Combivir alone. Additionally, combination of APS-1 and Combivir also alleviated the toxicity of Combivir. APS-1 not only increased the survival rate of mice administered with LD(50) dose of Combivir, but also reduced the hematologic toxicity induced by Combivir, RBC, HGB and PLT were restored to normal level. These results suggest that APS-1 had synergistic effect with Combivir, which provided new insight into the potential clinical use of polysaccharide sulfate in anti-AIDS field.