A plunging jet reactor (0.04-0.08 m3) was used for the production of the exopolysaccharide xanthan with Xanthomonas campestris. The microorganism was not affected by the pump shear force. Similar specific growth rates and xanthan space-time yields to those in other reactor types were achieved at much lower specific power input. The better oxygen sorption efficiency in the jet reactor overcompensated for the effect of poor mixing in the wall region at high xanthan concentrations.