Inhibitory effects of interferon-γ (γ-INF) and dexamethasone (Dexa) on growth of cultured fibroblasts were observed by MTT colorimetry, silver colloid technique of nucleolar of orgnizer regions associated protein (AgNORs) combined with image analysis and immunohistochemistry for type III collagen. The results showed that, (1) when γ-INF of 250×10,3,U/L and Dexa of 100mg/L were used, the inhibitory percentages of them on normal fibroblasts 3 days after culture were 43% and 33% respectively; (2) Above mentioned two inhibitors showed evident inhibitory effects on proliferation of normal, irradiated (on 3 or 5 days after irradiation) and 5-HT stimulated fibroblasts; (3) The third day after culture, the strongest inhibitory effects on fibroblasts AgNORs were observed when 250×10,3,U/L of γ-INF and 150mg/L of Dexa were delivered, the number of AgNORs granules in 5-HT stimulated fibroblasts decreased to 58% and 56% of normal control values; while the mean values of three quantitative parameters of AgNORs were also lower than those of control values; (4) The two inhibitors of above mentioned concentrations also demonstrated obvious restrained effect on the synthesis of type III collagen in 5-HT stimulated fibroblasts on day 3 after culture, the percentage of type III collagen positive fibroblasts were about 62% and 43% of control values.