The multifunctional cytokine interleukin‐6 (IL‐6) plays a central role in host defence mechanisms and hematopoiesis. Furthermore, dysregulation of IL‐6 gene expression is associated with the pathogenesis of various immunologically related diseases such as myeloma, systemic lupus erythematosus, rheumatoid arthritis, psoriasis and Kaposi's sarcoma. The regulation of IL‐6 gene expression occurs mainly at transcriptional level, although mechanisms of post‐transcriptional regulation have also been described. In the present study we demonstrate that in HeLa cells, induction of IL‐6 by interferon‐γ (IFN‐γ) is transcriptionally controlled, as shown by run on assays and analysis of the IL‐6 mRNA stability. Gel‐retardation experiments using antibodies specific for factors of the IRF family identified four protein‐DNA complexes, which bind to the interferon regulatory factor (IRF) binding site at position −267 to −254, in nuclear extracts from IFN‐γ treated cells. Furthermore, transient transfection analyses of the 5′‐flanking region of IL‐6 gene linked to the chloramphenicol acetyltransferase (CAT) reporter gene demonstrated that the −267 to −254 IRF site is necessary for IL‐6 induction by IFN‐γ. However, transfection experiments in which IRF‐1 and IxBα were overexpressed show that full‐scale transcriptional activation of the IL‐6 promoter directing CAT expression requires the co‐operation between IRF‐1 and NF‐xB at a low constitutive level.