Pleurotus florida was grown in shake-flask culture in liquid media containing different carbon and nitrogen sources. Changes in carbon and nitrogen supplies affected the amount of biomass and production of exocellular polysaccharide in the medium. Glucose was the preferred carbon source (20-60 g l(-1)) rather than sucrose, galactose, lactose, or xylose, for optimum exopolysaccharide production (0.5 gl(-1)) which was stimulated by a high C:N ratio. Nitrogen-limited cultures (0.1 gl(-1) ammonium tartrate) produced the most exopolysaccharide. Growth of P. florida in reactor cultures produced low yields of exopolysaccharide (0.29 gl(-1)), which was partly explained by the poor mass transfer rates associated with growth of mycelial pellets surrounded by adherent polysaccharide.