Cellulase-free xylanase was produced by Streptomyces sp. Ab106 on finely ground cane bagasse at 55 degreesC. The optimal medium composition was developed by applying the mixture design and linear mathematical program, and evaluated using the Plackett-Burman experimental design. The best composition of basal medium was found by using the mixture design method. The highest xylanase activity, 10.6 IU, was obtained after 6 days of fermentation in shaked flask at 100 rpm, 55 degreesC, pH 7. Both experimental designs showed that trace elements induced xylanase production. With fermentation in a 5-l fermenter, xylanase activity of 12.5 IU was achieved.