Xanthomonas campestris w.t. was used for production of xanthan gum in fermentations with chestnut flour for the first time. Fermentations were carried out with either chestnut flour or its soluble sugars (33.5%) and starch (53.6%), respectively, at 28 degrees C and 200 rpm at initial pH 7.0 in flasks. The effect of agitation rate (at 200, 400, and 600 rpm) on xanthan gum production was also studied in a 2-L batch reactor. It was found that xanthan production reaches a maximum value of 3.3 g/100 mt at 600 rpm and 28 degrees C at 45 h.