The human hepatitis B virus-X(HBV-X) was cloned into an expression vector, pET3d, containing a T7 promoter and direct expression was induced in Escherichia coli. The expressed HBV-V protein was purified to homogeneity by centrifugation, ion-exchange chromatography and gel filtration. After gel filtration, renaturation of HBV-X were performed using dialysis against serially diluted urea buffer. The biological activity of refolded HBV-X protein was confirmed by enhancement of protein/DNA complexes using gel-shift analysis.