A strain of Klebsiella oxytoca was isolated from milk capable of completely utilising the lactose (3.5%, w/v) in whey and producing biopolymer. In a broth containing 5% (w/v) lactose, 6.1 g/l of extracellular biopolymer was produced in 72 h by the isolate. At a shear rate of 2 s(-1), broth viscosities of greater than 400 cP were obtained in lactose rich (4%, w/v) media containing 0.2% (w/v) nitrogen concentration.