Although chronic renal insufficiency is the precursor to end-stage renal disease, few studies have examined the critical transition from advanced chronic renal insufficiency to end-stage renal disease. Basic and important questions, therefore, remain unanswered. For example: which patients with advanced chronic renal insufficiency are most likely to develop end-stage renal disease? How does cardiovascular disease evolve during the transition from advanced chronic renal insufficiency to end-stage renal disease? Howdo events and interventions during chronic renal insufficiency affect outcomes after onset of end-stage renal disease? The NIDDK-sponsored Chronic Renal Insufficiency Cohort (CRIC) study, which tracks a large cohort of individuals with chronic renal insufficiency, presents a unique opportunity to fill this important gap in knowledge. In this application, entitled "CRIC-Plus," we propose to intensify the study of patients who develop advanced chronic renal insufficiency and end-stage renal disease. Specifically, for patients whose glomerular filtration rate falls below 20 ml/min/1.73m2, renal function will be assessed every six months, additional echocardiograms at key clinical milestones will be performed and end-stage renal disease related parameters will be recorded. Our specific aims complement and substantially extend the core aims of CRIC. Aim #1: To determine the frequency of progression to end-stage renal disease compared with death from competing causes among patients with glomerular filtration rate below 20 ml/min/1.73m2 and to identify predictors of these different outcomes. Aim #2: To compare left ventricular structure and function when glomerular filtration rate falls below 20 ml/min/1.73m2 with left ventricular structure and function at the onset of end-stage renal disease. Aim #3: To compare predicted risks of cardiovascularevents, hospitalization and death using exposures measured when glomerular filtration rate falls below 20 ml/min/1.73m2 with predicted risks using exposures measured at the onset of end-stage renal disease. Aim #4: To study the effect of chronic renal insufficiency management, including the timing of dialysis initiation, on clinical outcomes after onset of end-stage renal disease.