Purpose: This study compared the effects of low and high weekly exercise frequencies on microvascular endothelium function and oxidative stress among patients with coronary artery disease. Methods: Thirty-four male patients completed a 6-month cardiac rehabilitation programme, from which 23 performed exercise with a high frequency (HF) and 11with a low frequency (LF). Systemic microvascular blood flow, maximal aerobic capacity, blood lipids, oxidative stress and anthropometric data were assessed prior to and after the cardiac rehabilitation programme. Microvascular blood flow was assessed in the skin of the forearm using laser speckle contrast imaging coupled with iontophoresis of acetylcholine.ResultsMaximal aerobic capacity, biochemical analysis and anthropometric data were similar between groups prior to and after the cardiac rehabilitation programme (P>0 05). However, after 6 months of cardiac rehabilitation performedwith HF, there was an increase in the peak response to acetylcholine compared with LF (83 5 58 5 versus 21 8 22 4%;P<0 05). Changes in lipid peroxida-tion (HF: 5 5 9 4 versus LF: 2 2 12 0 pmol MDA mg 1;P=0 19), cata-lase activity (HF: 0 07 0 17 versus LF: 0 04 0 08 U mg 1;P=0 74) andnitric oxide levels (HF: 1 8 15 3 versus LF: 3 2 12 3lM;P=0 36) were similar between groups after cardiac rehabilitation. Conclusion: Six months of aerobic exercise training performed with high frequencyis preferable to low frequency aiming endothelium microvascular function increases in patients with coronary artery disease. The mechanisms involved in this response are unclear and warrant additional research.