BACKGROUND A haemagglutinin was purified from Japanese Hokkaido red beans (Phaseolus vulgaris cv. Hokkaido red bean) with a procedure that included three chromatographic media. RESULTS Haemagglutinating activity was adsorbed on DEAE cellulose, Affi-gel blue gel and Mono S. The pure haemagglutinin was a homodimer and each subunit was around 30 kDa in molecular mass. The haemagglutinating activity of this agglutinin could not be inhibited by a variety of simple sugars at 200 mmol L(-1) concentration including alpha-L-fucose, D(+)-galactose, D(+)-glucose, D(+)-glucosamine, D(-)galactosamine, galacturonic acid, (+)-lactose, D(+)-melibose, L(-)-mannose, D(+)-mannose, D-mannosamine, D(+)-raffinose, L-rhamnose, (+)-xylose and galacturonic acid. The haemagglutinating activity was fully retained at pH 4-11 and at 0-80 degrees C, but was completely lost at extreme pH values (0-2 and 13-14) and at very high temperatures (90 degrees C and 100 degrees C). The haemagglutinin exhibited a weak mitogenic activity toward mouse splenocytes, a stronger anti-proliferative activity than Con A toward HepG2 (human hepatoma) cells and inhibited >80% of HIV-1 reverse transcriptase inhibitory activity at 3.3 micromol L(-1). It was devoid of anti-fungal activity. CONCLUSIONS Hokkaido red bean haemagglutinin possesses a potent anti-proliferative effect on HepG2 cells.