The culture supernatant of Candida albicans promoted the disruption of human red blood cells (RBCs). The haemolytic activity was detected in a sugar-rich fraction (about 200 kDa) from Sephacryl S-100 chromatography. As the haemolytic activity was adsorbed by concanavalin A-Sepharose, the haemolytic factor may be a mannoprotein. The activity was inactivated by periodate oxidation, indicating that the sugar moiety of the mannoprotein played an important role in the haemolysis. The structure of the sugar moiety of the mannoprotein was identified as a cell-wall mannan by 1H-NMR analysis, and purified C. albicans mannan promoted the disruption of RBCs. The binding of mannan to RBCs was demonstrated by flow cytometric analysis and was inhibited by the addition of band 3 protein inhibitor, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). The haemolysis caused by mannan was inhibited by DIDS, SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid) and bis(sulfosuccinimidyl) suberate, but not by pyridoxal 5-phosphate. These results indicated that a mannoprotein released from C. albicans bound to the band 3 protein on RBCs, thereby promoting their disruption.