INTRODUCTION: Individuals with kidney disease are at increased risk for coronary heart disease (CHD) and CHD is associated with an increased prevalence of chronic kidney disease (CKD). Awareness of CKD may potentially influence diagnostic decisions, life-style changes and pharmacologic interventions targeted at modifiable CHD risk factors. We describe here the degree to which persons with CHD are aware of their CKD. METHODS: The Reasons for Geographical and Racial Difference in Stroke (REGARDS) cohort study, a population-based sample of US residents aged 45 and older. We included in our analyses 28,112 REGARDS participants recruited as of June 2007. We estimated GFR (eGFR) using the MDRD equation, defined CKD as a GFR <60 ml/min/1.73 m(2), and ascertained awareness of chronic kidney disease and coronary heart disease through self-report. We used the odds ratio to compare the association between awareness of kidney disease, as measured by GFR <60 ml/min/1.73 m(2), among individuals with and without self-reported CHD by both the presence of CKD and the severity of impaired kidney function. RESULTS: Coronary heart disease was reported by 3,803 (14.1%) of subjects, and 11.3% of subjects had CKD by eGFR. Among all individuals with a GFR <60 ml/min/ 1.73 m(2), 9.6% reported having been told by a physician that they had kidney disease. Among those with CHD and CKD, 5.0% were aware of their CKD compared to 2.0% in those without CHD [OR (95% CI) = 2.57 (2.08, 3.28)]. This difference persisted after controlling for the level of kidney function [aOR (95% CI) = 1.87 (1.43, 2.41)]. CONCLUSION: There was a high prevalence of CKD and a low prevalence of awareness of kidney disease among older adults in the US population with or without coronary heart disease. These findings support recent recommendations that patients with cardiovascular disease be systematically screened for and educated about CKD.