Achyranthes bidentata polysaccharide sulfate (ABPS) was a sulfated derivate derived from Achyranthes bidentata polysaccharide (ABP) which was isolated and identified from Chinese herb Achyranthes bidentata. The anti human immunodeficiency virus type 1 (HIV-1) activities were studied in vitro and in vivo. ABPS was found to inhibit HIV-1 reverse transcriptase and integrase with the 50% inhibiting concentration (IC60) of (2.948 +/- 0.556) micromol x L(-1) and (0.155 +/- 0.030) micromol x L(-1), respectively, but the parent compound ABP was not effective. ABPS inhibited HIV-1 P24 antigen with IC50 of (0.082 +/- 0.044) micromol x L(-1) and selective index (SI) of > (358 +/- 148) in MT-4 cell cultures acutely infected with HIV-1 IIIB virus, and with IC50 of (11.80 +/- 5.90) micromol x L(-1) and SI of > (24.2 +/- 12.1) in PBMC cell cultures acutely infected with clinical isolated zidovudine resistant HIV-1 virus, but there was no activity even at its concentration of 500 micromol x L(-1) in latent infection of H9/HIV-1 IIIB cell cultures. 5% sera taken from rats after intraperitoneal injection from rats with ABPS 125 mg x kg(-1) once or mice with 3 mg x kg(-1) qd for 20 days effectively inhibited HIV-1 P24 in MT-4 cell cultures, but those had no inhibitory effect when given orally. The results suggested that ABPS is a promising HIV-1 inhibitor, active on HIV-1 reverse transcriptase, integrase in vitro and HIV-1 P24 antigens in cell cultures, it was well absorbed by intraperitoneal injection but poor in oral bioavailability. It warrants further study.