An extracellular polysaccharide producing bacterium Zoogloea sp. was isolated from marine environments. This strain could produce two different polysaccharides. One ( water-soluble polysaccharide : WSP) was from cell-free liquid medium, the other ( cell-bound polysaccharide : CBP) was obtained from cell surface. Both polysaccharides contained glucose, galactose and mannose as sugar components, but their molar ratios were different ( WSP : 2:2:3, CBP : 1:2:2) and half of the sugar components existed as uronic acid form. Both polysaccharide productions started at the early stage of the logarithmic growth phase. The amount of WSP and CBP was influenced by culture conditions such as additional carbon and nitrogen sources. Isolated Zoogloea sp. showed a high product yield without the increase of cell mass.