A bacterium Tomakomai B-l that was isolated from the activated sludge of a treatment process for wastewater of the pulp industry was found to produce soluble and insoluble exopolysaccharides (EPSs) when grown aerobically in a medium containing sucrose as the sole carbon source.. The sugar component of soluble EPSs consisted of rhamnose, mannose, galactose, glucose, mannuronic acid, galacturonic acid and glucuronic acid, and that of insoluble EPSs consisted of rhamnose, mannose, galactose, glucose, mannuronic acid and glucuronic acid. The concentrations of insoluble and soluble EPS were approximately 1.63 and 2.58 g/l respectively, by Erlenmeyer flask culture at 20 degrees C for 3 d with a synthetic medium containing 1% sucrose, 0.05% CaCO3,, 0.05% MgSO4, 0.1% K2HPO4, 0.0001% Na2MoO4, 0.01% urea, 1.07% MES and small amounts of trace metals. Tomakomai B-l was identified as Rahnella aguatilis. To our knowledge the production of EPSs by R. Aquatilis is reported here for the first time.