Background/Aims: Both TGF-β and cyclooxygenase-2 have been implicated in the pathogenesis of interstitial fibrosis in unilateral ureteral obstruction (UUO). Cyclic tensile stretch has been used in vitro to mimic the changes in intrarenal pressure in UUO. We sought to determine the effect of meloxicam (a selective cyclooxygenase-2 inhibitor) on extracellular matrix and TGF-β synthesis in stretched renal fibroblasts (NRK-49F). Methods: NRK-49F cells were subject to cyclic stretch (6 cycles/min, 15% elongation) using a Flexcell apparatus. Cells were stretched in the absence or presence of meloxicam for 48 h, and then cells and supernatants were isolated. Collagen was quantified by the Sircol assay; fibronectin and laminin were visualized using immunofluorescence. TGF-β was quantified by ELISA, and protease activity determined by a colorimetric assay. Results: Bothcollagen and TGF-β synthesis were increased following a 48-hour stretch of NRK-49F. Meloxicam significantly decreased the collagen and TGF-β response to stretch. Stretch-induced fibronectin and laminin synthesis was also decreased by meloxicam. NRK-49F protease activity was decreased by stretch; this was unaffected by meloxicam. Conclusions: Stretch of NRK-49F results in extracellular matrix synthesis, a process which may be activated in UUO and contribute to interstitial fibrosis. Inhibition of cyclooxygenase-2 may reduce fibrosis through a TGF-β-dependent process.