Two xylanases, designated XylA and XylB, were purified from the culture supernatant of the alkaliphilic Bacillus sp. strain AR-009. The molecular masses of the two enzymes were estimated to be 23 kDa (XylA) and 48 kDa (XylB) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum pHs for activity were 9 for XylA and 9 to 10 for XylB. The temperature optima for the activity of XylA were 60 degreesC at pH 9 and 70 degreesC at pH 8. XylB was optimally active at 75 degreesC at pH 9 and 70 degreesC at pH 8. Both enzymes were stable in a broad pH range and showed good stability when incubated at 60 and 65 degreesC in pH 8 and 9 buffers.