The production and rheology of exomannan by the yeast Rhokotorula mucilaginosa YR-2 was studied. Cultures were incubated at 30°C in medium (sucrose: 100 g/L; ammonium sulfate: 20 g/L). Fermentation used a 10-liter fermentor aerated at 1 vvm, and 550 rpm. During culture, the pH was adjusted to 1.8 with ammonia solution. The maximum amounts of exopolysaccharide (7.8 g/L) and biomass (39.2 g/L) were obtained at 120 h. This mannan was much less viscous than other polysaccharides, and had excellent physical stability in terms of pH, freezing, and NaCl concentration.