Factors predicting the efficacy of Interferon (IFN) therapy were studied in 137 (62 sustained responders, SR, and 7 5 non-responders, NR) cases with chronic hepatitis C, in whom laparoscopy was done following IFN therapy. Univariate analysis demonstrated statistically significant differences in pre-IFN therapy levels of alanine aminotransferase (ALT), HCV genotype and laparoscopic findings between the SR and NR. The SR rate in cases with Code numbers (Code Nos.) 20 1, 20 1.5 and 20 1.6 was 69.2% and that in cases with Code Nos. 3 1 7 and 3 1 7.4 was 10.7%, both being statistically significant in relation to other Code No. groups. Multivariate analysis was conducted in only 54 cases and statistically significant differences were demonstrated for laparoscopic findings (Odds ratio 0.051, p=0.037) and HCV genotype (Odds ratio 0.083, p=0.012). These factors were considered useful for predicting the efficacy of IFN therapy. Laparoscopic changes after IFN therapy in the SR group were studied in 12 cases, in whom increments in whitish markings and the appearance of peliosis hepatis were observed in 75% and 42%, respectively, whereas the values in nine NR group cases were 1 1 % and 0%. These findings differed significantly between the SR and NR groups (both, p<0.05) and were thought to be characteristic of SR. (Dig Endosc 1996 ; 8 : 293-301)