Depending on the reduction in glomerular filtration rate (GFR) as a measure of renal insufficiency and depending on their age, patients with chronic kidney disease have a 1.5 to 1,000-fold higher cardiovascular risk. Renal insufficiency is inherently an independent risk factor for cardiovascular events, which is likewise the case for patients also presenting with hypertension or diabetes mellitus. When cardiac insufficiency or coronary heart disease is already manifest, the GFR is the most important predictive factor for the patients' further survival. Proteinuria or albuminuria as signs of kidney disease are also important markers and correlate with the cardiovascular risk in the range of both macro- and microalbuminuria. Endothelial dysfunction, oxidative stress, dyslipidemia, and increased atherosclerosis are being discussed as pathophysiological mechanisms of elevated cardiovascular risk.