Acute kidney injury (AKI), previously termed acute renal failure, is associated with increased mortality, prolonged hospital stay, and accelerated chronic kidney disease (CKD). Over the past 2 decades, dramatic rises in the incidences of AKI have been reported, particularly within the United States. The question arises as to whether these changes reflect actual increases in disease incidence, or are potentially explained by the introduction of consensus definitions that rely on small standardized changes in serum creatinine, changes in coding and reimbursement, or increasingly available and more liberal use of dialysis. In this review, we explore the secular trends in AKI incidence in North America and Western Europe and its potential contributors.