The gene for the DNA-binding protein Sso10a from the hyperthermophilic archaeon Sulfolobus solfataricus was cloned and overexpressed in Escherichia coli. Crystals of the purified protein have been grown that diffract to beyond 2.15 A resolution. The protein crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 57.24, b = 60.16, c = 69.96 A. With one dimer per asymmetric unit, the crystal to volume per protein mass (V(M)) is 2.9 A(3) Da(-1) and the solvent content is approximately 57%. Complete X-ray diffraction native data were collected from a single crystal and processed to 2.15 A.