Xanthan gum were produced from the following Xanthomonas strains; standard strain Xanthomonas campestris NRRL B-1459 and isolated strains Xanthomonas arbicola pv. juglandis, Xanthomonas axonopodis pv. vesicatoria, Xanthomonas axonopodis pv. begonia, Xanthomonas axonopodis pv. dieffenbachia. The viscosity features of the xanthan gums obtained were determined at 25-80 degrees C with different pH values and were compared to commercial xanthan gum. Our results indicate that X. arbicola pv. juglandis showed the highest productivity (8.22 +/- 1.52 g/L gum). This was followed by X. axonopodis pv. begonia (7.74 +/- 1.30 g/L gum), and the control bacterial strain X. campestris NRRL B-1459 (7.46 +/- 0.28 g/L gum). X axonopodis pv. vesicatoria showed the lowest productivity (6.40 +/- 0.55 g/L gum). No xanthan gum could be obtained from X. ayonopodis pv. dieffenbachia. Xanthan gum produced by X. axonopodis pv. vesicatoria showed the highest viscosity value (428 mPa.sec at 1% Solution) in all Xanthomonas strains isolated from plants.