Monocyte chemoattractant protein-1 (MCP-1), a potent monocyte chemoattractant synthesized by vascular cells and monocytes, has been proposed to be an important mediator of inflammatory responses in the arterial vasculature. It was recently demonstrated that hypertension is associated with an inflammatory response in the arterial wall. To determine the effect of hypertension on arterial MCP-1 expression, we induced hypertension in Sprague-Dawley rats by infusing angiotensin II (0.75 mg · kg⁻¹ · d⁻¹ SC) for 7 days. Using Northern blot analysis, we detected a 3.6-fold increase in MCP-1 mRNA in the aortas of hypertensive rats. When we normalized blood pressure in angiotensin II–treated rats through oral administration of the nonspecific vasodilator hydralazine (15 mg · kg⁻¹ · d⁻¹), aortic MCP-1 mRNA expression was significantly reduced. Similar results were obtained with a norepinephrine model of hypertension. Taken together, these data suggest that mechanical factors may be responsible in part for the upregulation of expression. Consistent with this interpretation, we found that cultured rat aortic vascular smooth muscle cells exposed to mechanical strain (20% peak deformation at 1 Hz) exhibited a marked increase in MCP-1 expression, suggesting the hemodynamic strain imparted onto arterial cells in hypertension is an important stimulus underlying this phenomenon. These results provide important insights into the in vivo regulation of MCP-1 and have potential implications for understanding the influence of hypertension on atherosclerosis.