Transforming growth factor-b1 contributes to vascular diseases resulting from smooth muscle cell (SMC) proliferation and migration. The stress protein heme oxygenase-1 (HO-1) catabolises the heme to the vasodilator carbon monoxide and the antioxidant biliverdin. Endogenous antioxidant pathways such as HO-1 and glutathione (GSH) serve as adaptive responses to limit oxidative stress. We have investigated whether TGF-b1 modulates HO-1 expression and GSH levels, and activation of the transcription factor Nrf2 and mitogen activated protein kinases (MAPK). Cultured human aortic SMC were treated with TGF-b1 (0–10 ng/ml, 0–24h) and HO-1 and Nrf2 expression or phosphorylation of ERK1/2, p38MAPK and JNK determined by western blot analyses. Reduced GSH levels were analysed using a fluorescence assay. Translocation of Nrf2 was also assessed by immunofluorescence and superoxide production measured by lucigenin chemiluminescence. TGF-b1 (2.5 ng/ml, 4h) induced phosphorylation of JNK and p38MAPK but not ERK1/2 and increased superoxide generation. HO-1 levels were elevated by TGF-b1 (5 ng/ml, 8–12 h). Nuclear Nrf2 expression was increased by TGF-b1 (2h, 5 ng/ml), however GSH levels were unaltered. These findings provide novel mechanistic insights for the actions of TGF-b1 in vascular diseases. Supported by the Guy's & St Thomas' Charitable Foundation and British Heart Foundation.