To the Editor In their recent study, Hewitt et al1 found that the prevalence of burnout varied dramatically (from 3.2% to 91.4%) depending on how the syndrome was defined. The authors’ observations resonate with long-lamented problems in the conceptualization and measurement of burnout.2,3 Even the most basic aspects of the definition of burnout have remained disputed despite nearly 50 years of research on the syndrome. Researchers have failed to establish firm diagnostic criteria for burnout, leaving unresolved the key question of what constitutes a case. This situation has been a hindrance to occupational health decision makers, who need to base their actions on clear, clinically founded information. Considerable resources have been dedicated to burnout research for a return on investment that is difficult to identify in terms of health promotion.