The cDNA of human augmenter of liver regeneration was subcloned onto the downstream of the P(R)P(L) promoter of the expression plasmid pBV220. The recombinant plasmid could stably express ALR with high efficiency (up to 20% of the total bacterial proteins) in E. coli through thermal induction. The expressed recombinant ALRs could produce a significant increase in the incorporation of (3)H-TdR into liver DNA of a 1/3 hepatectomized test animal and also had a potent antihepatitis effect. These results suggest that ALR appears to be an important regulator of liver regeneration and may be used in clinical trial for enhancing liver regeneration in the treatment of hepatic diseases.