E. coli cells expressing recombinant human interferon-gamma was disrupted by sonication and dissolved in 7mol . L(-1) guanidine hydrochloride. The extract obtained was then renaturated by 70-fold dilution with PBS. HuIFN-gamma was purified by affinity chromatography with monoclonal antibody from the renaturated crude feed solution. After washing the column with PBS, the adsorbed HuIFN-gamma was eluted with PBS containing 0.5mol . L(-1) NaCl. The column was regenerated with 2mol . L(-1) GuHCl for reuse. After one step of affinity purification the purity of interferon-gamma was over 95%, and the specific activity of the HuIFN-gamma reached 1.2x10(7) IU . mg(-1) protein. 92.8% of recovery was obtained in the elution step. Total recovery of HuIFN-gamma activity in the affinity chromatography was 78%.