© 2015 Ikdahl et al. Introduction: Endothelial dysfunction is an early step in the atherosclerotic process and can be quantified by flow-mediated vasodilation (FMD). Our aim was to investigate the effect of long-term rosuvastatin therapy on endothelial function in patients with inflammatory joint diseases (IJD) with established atherosclerosis. Furthermore, to evaluate correlations between change in FMD ($Δ$FMD) and change in carotid plaque (CP) height, arterial stiffness [aortic pulse wave velocity (aPWV) and augmentation index (AIx)], lipids, disease activity and inflammation. Methods: Eighty-five statin-näive patients with IJD and ultrasound-verified CP (rheumatoid arthritis: n = 53, ankylosing spondylitis: n = 24, psoriatic arthritis: n = 8) received rosuvastatin treatment for 18 months. Paired-samples t tests were used to assess $Δ$FMD from baseline to study end. Linear regression models were applied to evaluate correlations between $Δ$FMD and cardiovascular risk factors, rheumatic disease variables and medication. Results: The mean ± SD FMD was significantly improved from 7.10 ± 3.14 % at baseline to 8.70 ± 2.98 % at study end (p textless 0.001). Improvement in AIx (p textless 0.05) and CP height reduction (p = 0.001) were significantly associated with $Δ$FMD (dependent variable). Conclusions: Long-term lipid lowering with rosuvastatin improved endothelial function in IJD patients with established atherosclerotic disease. Reduced arterial stiffness and CP regression were longitudinally correlated with the improvement in endothelial function measured by FMD. Trial registration: ClinicalTrials.gov NCT01389388. Registered 16 April 2010.