As childhood obesity is increasing, its affects on the cardiovascular system remain unclear. Cyclooxygenase (COX) enzymes metabolize arachidonic acid (AA) into vasoactive prostanoids and their expression is altered in hypertensive animal models. We hypothesized that there would be augmented vasoconstriction to AA, mediated via COX 1 in rats fed a high-fat (HF)-diet for 10 weeks (from 3 to 13 weeks old) compared to those fed regular rat chow. AA induced vasoconstriction was augmented in the aorta from rats fed a HF-diet compared to control. Inhibitors to AA metabolism suggest that COX 1 activity predominates in rats fed a HF-diet. Western blot analysis showed that COX 1 but not COX 2 protein expression was increased in aortic rings stimulated with AA from the rats fed the HF-diet. These results suggest that vasoconstriction induced by AA is augmented in rats fed the HF-diet due to increased COX 1 expression and activity.