The present study examined the efficacy and the predicting factors of response to interferon (IFN) alpha in patients with liver cirrhosis associated with hepatitis type C virus infection (LC type C). Sixty-seven patients were treated with IFN alpha and were classified into 2 Groups. Group 1 : Patients with liver cirrhosis, showing histological liver cirrhosis or chronic active hepatitis with lobular disorganization. Group 2 : Patients with chronic hepatitis, showing histological chronic persistent hepatitis or chronic active hepatitis without lobular disorganization. Sustained response to IFN was obtained in 5/17 (29.4%) and 24/50 (48%) of patients in Group 1 and Group 2, respectively. However, the difference was not significant. All patients in Group 2 showed a significant decrease in alanine aminotransferase (ALT) levels during the treatment, whereas 5 of the 17 patients in Group 1 showed no response. All sustained responders in Group 1 who were tested for serum HCV-RNA titer showed low serum HCV-RNA titer, which was less than 10^7 copies/ml, while all except one patient of the non-responders of Group 1 showed above 10^8 copies/ml. It is said that patients with LC type C are more resistant to IFN treatment compared to those with chronic hepatitis type C. However, our findings suggest that even in patients with LC type C, low serum HCV-RNA levels might be associated with better response to IFN.