AIM: To assess the effect of artificial liver support system (ALSS) on patients with severe viral hepatitis, who were divided into treatment group and control group.METHODS: Four hundred in-hospital patients enrolled during 1995-2003 who received ALSS therapy were studied as the treatment group. Four hundred in-hospital patients enrolled during 1986-1994 who received other medical therapies served as the control group. The methods of ALSS used included plasma exchange, hemoperfusion,hemofiltration, continuous hemodiafiltration (CHDF). The effect of ALSS treatment was studied in patients at different stages of the disease.RESULTS: The cure rate of acute and subacute severe hepatitis in the treatment group was 78.9% (30/38), and was 11.9% (5/42) in the control group. The improved rate of chronic severe hepatitis in the treatment group was 43.4% (157/362), and was 15.4% (55/358) in the control group.We found that patients treated with ALSS in the early or middle stage of the disease had much higher survival rates than patients in the end stage of the disease.CONCLUSION: ALSS is an effective and safe therapy for severe viral hepatitis.