Alpha-glucan L-FV-II and beta-glucan L-FV-I were shown to co-exist in the extract of fruiting bodies of Lentinus edodes with aq. 5% NaOH/0.05% NaBH4 in previous work. Water-insoluble alpha-(1-->3)-D-glucan (L-FV-II) was treated with sulfur trioxide-pyridine complex at 25 degrees C to synthesize the water-soluble sulfated derivative SL-FV-II with a degree of substitution (DS) 1.1 in non-selective sulfation. The weight-average molecular weight (Mw) of sulfated glucan SL-FV-II is 57% of that of the original alpha-glucan L-FV-II. The alpha-glucan administered by gavaging at a dose of 50 mg/kg of body weight to BALB/C mice having implanted solid Sarcoma 180 was effective at an inhibition rate of 42%. In vitro experiments using human and murine tumor cell lines showed that SL-FV-II had antiproliferation activity at the concentration of 20 microg/mL towards four tumor cell lines. The sulfated alpha-(1-->3)-D-glucan had potent antiproliferation action (52%) on human MCF-7 breast carcinoma cells.