Chronic obstructive pulmonary disease (COPD) and asthma are conditions that exact a tremendous toll on patients, providers, and society. The substantial increase in the prevalence of both conditions in recent decades has generated sizable concern from both domestic and global perspectives. The underlying characteristics of both conditions involve inflammation of the respiratory tract, although the specific nature and reversibility of these processes differ according to each illness. Within the context of disease management, acute exacerbations are important clinical events that contribute to an increase in morbidity and mortality, and may occur in any patient suffering from the disease. Because these conditions are highly important to clinical practice and healthcare systems, this article will highlight key aspects of epidemiology, burden of illness, and clinical presentation of COPD and asthma. A review of the definition, classification, and natural history is also offered, emphasizing the role of acute exacerbations. In general, the natural history of both COPD and asthma is highly variable and not precisely defined because of their heterogeneous clinical courses. Continued inquiry concerning the epidemiology, etiology, classification, and prognosis of each condition and related exacerbations may offer clinicians improved decision-making information to optimize interventions for affected patient populations.