A novel lectin Agrocybe aegerita antiviral protein (AAVP) was purified, from the fruiting bodies of edible fungus Agrocybe aegerita by precipitation of 40%��80% (NH 4) 2SO 4 followed by DEAE SepharoseFast Flow and Sephacryl S 200 chromatography. The relative molecular mass of AAVP was 32 kD tested by gel filtration, the subunit of AAVP was 15 8 kD determined by SDS PAGE. Its pI was about 3 8 by isoelectric focusing. AAVP is probably unglycosylated and blocked by pyroglutamyl at the N terminus. The amino acid sequence of the N terminus was QGVNIYNIVAGA, and the sequence of a segment of AAVP obtained after being digested by trypsin was PDGPWLVEKR. AAVP agglutinated 3 types of human and 12 types of animal erythrocytes regardless of blood group or category. However, its hemagglutinating activity for mammalian erythrocytes is much higher than that for bird and aquatic. In a hemagglutination assay, porcine mucin was the only inhibitor of the lectin among the 18 sugars and 3 glycoconjugates tested. AAVP was thermal stable, acid stable and alkali stable. Its activity was unaffected by demetalization and addition of divalent metals including CaCl 2, MgCl 2 or ZnCl 2. AAVP had inhibiting effect on tumor cell lines SGC 7901, MGC 80 3, BGC 823 and leucocythemia cell line HL 60 in vitro . AAVP is toxic to mouse by celiac injection with an LD 50 of 15.85 mg /kg body weight.