An elevation in blood glucose concentration leads to increased risk of developing diabetes-associated atherosclerotic cardiovascular disease due to an excessive accumulation of cholesterol in arterial macrophages. ATP-binding cassette transporter A1 (ABCA1) is an atheroprotective protein that mediates the export of cholesterol from macrophages. The present study aims to investigate the effect of hyperglycemia on the regulation of ABCA1 expression and to explore its underlying mechanisms of regulation in macrophages. Our results show that high glucose activates the extracellular signal-regulated kinases (ERK) signaling pathway via reactive oxygen species (ROS) production, which in turn down-regulates ABCA1 mRNA and protein expression. This down-regulation is mediated by accelerating ABCA1 mRNA and protein degradation in macrophages exposed to high concentrations of glucose. Our results provide evidence for the first time that hyperglycemia inhibits ABCA1 expression by ERK-modulated ABCA1 mRNA and protein stability. Overall, these results provide a mechanism for hyperglycemia-induced reduction in ABCA1 expression, which suggests a promising strategy for the treatment of diabetes-associated atherosclerosis. J. Cell. Biochem. 114: 1364–1373, 2013. © 2012 Wiley Periodicals, Inc.