To evaluate the role of the proinflammatory cytokines IL-4 and OSM in the fibrotic process, we evaluated in vitro the expression level of genes coding for ECM components (collagen 1A1 and 1A2) and αSMA (indicator of myofibroblast transition) both at the transcriptional and protein levels in cytokine-stimulated nasal-polyp-derived fibroblasts. The gene discussed is IL4; the disease is nasal cavity polyp.