When patients develop acute kidney injury, a small fraction of them will develop end-stage renal disease later. The severity of renal impairment in the remaining patients is uncertain because studies have not carefully examined renal function over time or the precise timing of entry into a late stage of chronic kidney disease. To determine these factors, we used a United States Department of Veterans Affairs database to ascertain long-term renal function in 113,272 patients. Of these, 44,377 had established chronic kidney disease and were analyzed separately. A cohort of 63,491 patients was hospitalized for acute myocardial infarction or pneumonia and designated as controls. The remaining 5,404 patients had diagnostic codes indicating acute renal failure or acute tubular necrosis. Serum creatinine, estimated glomerular filtration rates, and dates of death over a 75-month period were followed. Renal function deteriorated over time in all groups, but with significantly greater severity in those who had acute renal failure and acute tubular necrosis compared to controls. Patients with acute kidney injury, especially those with acute tubular necrosis, were more likely than controls to enter stage 4 chronic kidney disease, but this entry time was similar to that of patients who initially had chronic kidney disease. The risk of death was elevated in those with acute kidney injury and chronic kidney disease compared to controls after accounting for covariates. We found that patients who had an episode of acute tubular necrosis were at high risk for the development of stage 4 disease and had a reduced survival time when compared to control patients.