The humar gene encoding for the histone-like DNA-binding protein HU from the hyperthermophilic eubacterium Thermotoga maritima was efficiently overexpressed in Escherichia coli under the T7 promoter. The HU protein was purified using SP-Sepharose ion-exchange and heparin-affinity chromatography and was successfully crystallized in ammonium sulfate. The crystals were grown in the tetragonal form in space group P43 or P41 and have unit-cell dimensions a = b = 46.12, c = 77.56 Å, a = β = γ = 90°. The crystals diffract X-rays to 1.6 Å resolution using synchrotron radiation and are suitable for determination of the HU structure at high resolution.