Heart failure (HF) has emerged as a major public health issue and is among the most significant causes of morbidity and mortality for older adults in Western countries. Acute HF syndromes (AHFS) encompass many important etiologies and comorbidities. There are several different clinical definitions and classifications of AHFS that are based on their clinical picture and pathophysiology. These definitions and classifications should, at best, serve to individually tailor diagnostics and therapy. Another important application of these definitions and classifications is to help guide future clinical trials in AHFS. The epidemiology of AHFS has been studied in large and small registries and surveys in both North America and Europe. The properties of the population of patients with acute HF are discussed in light of these data.