Xylanases being used for several industrial processes under harsh conditions must be robust. A Streptomyces sp. SU9 isolated from humus was found to produce highly thermoactive (optimum temperature 80 degrees C) and alkali-stable (optimum pH 9.0) xylanase. The organism not only utilized agricultural-based carbon sources like wheat bran and wheat straw, but produced xylanase titre (5200 IU/L) higher than that obtained on pure xylan (2600 IU/L), rendering economy to production and application. Yeast extract as nitrogen source promoted maximum xylanase production compared to soybean meal and peptone. The xylanase was stable over a pH range of 6-9. Therrnoactivity of xylanase was moderate as it inactivated upon incubation above 60 degrees C for 30 min.