Technical Abstract: Background: Intake of industrial trans fatty acids (TFA) has been positively associated to systemic markers of low-grade inflammation and endothelial dysfunction in cross-sectional studies, but results from intervention studies are inconclusive. Objective: To examine the effect of a high intake of TFA on systemic biomarkers of inflammation and endothelial dysfunction, adipose tissue expression of adipokines and content of ceramide and urinary markers of oxidative stress. Design: A 16-weeks double-blind parallel intervention study where 52 healthy overweight postmenopausal women were randomized to receive either partially hydrogenated soybean oil providing 15.7 g per day of TFA or a control oil where TFA was replaced by mainly oleic and palmitic acid. Results: After 16 weeks TFA intake increased baseline-adjusted serum tumor necrosis factor (TNF) a by 12 % (95% confidence interval (CI): 5 - 20%; P= 0.002) more in the TFA group compared to controls. Plasma soluble TNF receptors 1 and 2 were also increased by TFA [155 (CI: 63 - 247) pg/ml; P<0.001 and 480 (CI: 72 - 887) pg/ml; P=0.02, respectively]. Serum C-reactive protein, interleukin (IL) 6 and adiponectin and adipose tissue mRNA expression of IL6, IL8, TNFa and adiponectin and ceramide content were not affected by the dietary intervention, neither was the urinary marker of oxidative stress 8-iso-prostaglandin-F2a. Conclusions: This dietary trial shows that the mechanisms linking dietary TFA to cardiovascular disease is likely to involve induction of low-grade systemic inflammation although this is not mirrored in adipose tissue mRNA expression within 16 weeks.