Ischaemic heart disease (IHD) and degenerative brain disease are two major sources of death and disability affecting all countries. While the consequences of obstructive disease in major vessels supplying blood to both organs have been widely documented, less attention has been paid to disease processes affecting the microcirculation that may affect cardiac and cerebral function. Yet, over the last decade significant progress has been made in understanding the substrate of microvascular disease in both organs. In the heart, arteriolar thickening and capillary rarefaction that reduce the conductance of the microvasculature and its ability to vasodilate in response to increased myocardial oxygen demands constitute the leading cause of coronary microvascular dysfunction (CMD). In the brain, concentric hyaline thickening of deep penetrating small arteries (arteriolosclerosis) with associated fibrosis of the vessel wall constitutes the most frequent substrate for cerebral small vessel disease (CSVD). Of note, both CMD and CSVD share common risk factors, such as age, hypertension, and diabetes.3 These factors might have a common effect on the microvascular domain of cardiac and cerebral vascular beds. Although a potential link between both conditions has been hypothesized based on the similarities between pathological changes and risk factors, advance in knowledge exploring this has been hampered by lacking objective evidence of CMD and pathological brain changes indicative of CSVD in prior research studies. Thus, the relationship between CMD and CSVD is unknown. The main objective of this study was to analyse the relationship between cerebrovascular disease and CMD in patients with atherosclerotic coronary artery disease (CAD).