Cyclosporine, a calcineurin inhibitor, is a potent immunosuppressive agent that acts chiefly through the inactivation of T-lymphocytes. Several clinical studies have demonstrated the effectiveness of cyclosporine for treating fibrotic lung disease, but the underlying mechanism remains elusive. We hypothesized that cyclosporine exerts direct effects against fibrogenesis of lung myofibroblasts, and aimed to elucidate the mechanism of this anti-fibrotic effect through gene-expression profiling using DNA microarray analysis. We found that cyclosporine suppressed the expression of alpha-smooth muscle actin and collagen type I in myofibroblasts that had been differentiated from a fetal human lung fibroblast cell line by induction with transforming growth factor (TGF)-β. Furthermore, microarray analysis revealed that cyclosporine down-regulated 57 genes whose expression levels were increased by TGF-β, and up-regulated 73 genes, whose expression was decreased by TGF-β. Classifying these 57 down-regulated and 73 up-regulated genes with the Database for Annotation, Visualization and Integrated Discovery (DAVID) web tool, we have identified the involvement of several functional categories, including innate immunity, cytokine interaction, growth factor, and cancer pathway. Of the identified genes, we selected three fibrosis-related genes, insulin-like growth factor binding protein 2 (IGFBP2), inhibitor of DNA binding 1 (ID1) and peroxisome proliferator-activated receptor gamma (PPARG), and validated their expression patterns by quantitative reverse transcription-polymerase chain reaction. Cyclosporine treatment decreased the expression levels of IGFBP2 and ID1, but increased PPARG expression. These results suggest that cyclosporine is a potent anti-fibrotic agent acting on myofibroblasts. Therefore, cyclosporine shows potential as a novel remedy for fibrotic lung disease.