To investigate the possible mechanisms that might be involved in the induction of pulmonary fibrosis associated with granulomatous inflammation, we measured the mRNA expression of TGF-β1, TIMP-1, and IL-4, which are thought to be involved in induction of pulmonary fibrosis, during the fibrotic stage in sarcoid-fibrotic mice. The gene discussed is IL4; the disease is pulmonary fibrosis.