Recently, the role of cytokines in controlling gene expression of connective tissue components has been increasingly emphasized. Many cytokines have been shown to have specific effects on gene expression of connective tissue components, and the roles of cytokines in controlling connective tissue metabolism during wound healing and in fibrosis have increasingly been discussed. In this article, the effects of cytokines on regulation of gene expression of connective tissue components, especially of type I collagen were described. We analysed transcriptional control of the alpha 1(I) collagen gene by TNF-alpha by means of DNA mediated transfection experiments using recombinant plasmids in which the promoter region of the human alpha 1(I) collagen had been fused to the chloramphenicol acetyl-transferase (CAT) gene, in human dermal fibroblasts. It was found that TNF-alpha reduced alpha 1(I) collagen transcription through at least up to -107 bp upstream of the human alpha 1(I) collagen promoter gene in dermal fibroblasts.