beta-Xylanase from Streptomyces olivaceoviridis E-86 has been crystallized by the hanging drop vapor diffusion method from 25% saturated ammonium sulfate and 2% McIlvaine buffer, pH 5.7. The crystals diffract to at least 1.9 A resolution, and belong to space group P2(1)2(1)2(1), with unit-cell dimensions of a=79.6 A, b=95.2 A, and c=140.3 A. There are probably two xylanase molecules (MW=45 K) per asymmetric unit.