A fully active 83-kDa truncated form of recombinant hyaluronate lyase from Streptococcus pneumoniae was crystallized by the hanging drop vapor diffusion method using ammonium sulfate as a precipitating agent. Crystals grew at room temperature using a variety of buffers with pH around 6. The crystals diffract X-rays beyond 2.0 A resolution using Cu K alpha radiation and a rotating-anode X-ray source. They belong to the orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions, a = 84.2, b = 104.2, c = 104.6 A, and alpha = beta = gamma = 90.0 degrees. The VM value of 2.9 A3/Da is consistent with only one molecule of the enzyme in the asymmetric unit and the solvent content of 57%. Diffraction data 94.7% complete to 2.0 A resolution with Rsym of 5.4% were collected from one native crystal at room temperature. The search for heavy-atom derivatives to solve the structure is in progress.