OBJECTIVE To study the influence and mechanism of gamma-IFN on fibroblasts in hypertrophic scars(HTS). METHODS The cultured fibroblastic cells were isolated from the hypertrophic scars of 10 patients. The fibroblasts were divided into two groups, one group was treated with gamma-IFN (100 U/ml, 5 days) and the other without gamma-IFN as control. The proliferative activity in both groups was investigated and compared by blood cytometer, the proportion of myofibroblast (MFB) and the ratio of apoptosis were examined and analysed between two groups by flow cytometry using alpha-smooth muscle actin (alpha-SMA) as marker. RESULTS The proliferative activity was downregulated with gamma-IFN. In gamma-IFN treated group, the differentiation of MFB were reduced and the decreasing ratio was 3.2% at the 2nd day and up to 10.5% at the 8th day, then it reduced gradually. The apoptosic ratio is 17.7% in gamma-IFN treated group, and is 10.9% in control group. The difference was statistically significant. CONCLUSION gamma-IFN could downregulate the proliferation of fibroblasts, decrease the differentiation of MFB and induce the apoptosis. It has beneficial effect in the treatment of hypertrophic scars(HTS).