Supervised Exercise-based Cardiac Rehabilitation (ECR) is recommended for patients with Ischemic Heart Disease (IHD). Vascular inflammation is an important pathophysiological factor in development of IHD and cardiovascular events. The aim of this study was to investigate whether an extended 12-week ECR program was more successful in reducing low-grade vascular inflammation, compared to a conventional 8-week ECR program. A total of 110 patients treated for IHD, and referred to ECR, were randomized to a 12-week or 8-week ECR intervention. We measured the concentration of soluble vascular cell adhesion molecule 1 (sVCAM-1), interleukin-6 (IL-6), highsensitivity C-reactive protein (hsCRP), before and after participation in either of the two ECRs and at 6-month and one year follow-up. Additionally, we determined the absolute White Blood Cell count (WBC), the absolute monocyte count, and the monocyte sub populations. For the primary outcome (sVCAM-1), we observed no differences between groups on a short and long-term basis. At 1-year follow-up, there were no differences in IL-6, hsCRP, WBC and monocytes. However, in the 12-week ERC group more inflammatory biomarkers were significantly reduced at the end of ECR (IL-6: p=0.002; hsCRP: p< 0.00001; CD14++CD16- classical monocytes: p=0.0178), compared to the 8-week ECR group. On a short time basis, 12-week ECR reduces significantly more inflammatory biomarkers in comparison with an 8-week ECR program. However, this effect was not sustained on a long-term basis, probably due to an underpowered study design. Further studies on optimizing ECR program duration and frequency are needed to evaluate the effects for the vascular inflammatory biomarkers.