The mushroom Paecilomyces japonica, grown on the silkworm larvae, has been used in Asia as a nutraceutical, tea, and Chinese medicine. In the present study, a sialic acid-specific lectin has been purified from the mushroom P. japonica using affinity chromatography on a fetuin-agarose column. Electrophoretical analyses indicated that this lectin, designated P. japon ica agglu tinin (PJA), is an acidic protein with a molecular mass of 16 kDa, and has no intermolecular disulfide bonds. PJA induced hemagglutination activity in human ABO, mouse, rat, and rabbit erythrocytes. This activity was inhibited by sialic acid and sialoglycoproteins, but not by any other carbohydrates. PJA was stable at pH 4.0-8.0, and at temperatures below 55°C. The activity of PJA was independent of EDTA and divalent cations. In addit ion, PJA exerts cytotoxic effects on the following cancer cell lines: human stomach cancer SNU-1, human pancreas cancer AsPc-1, and human breast cancer MDA-MB-231.