Chronic Fatigue Syndrome (CFS) is a new challenge to health care professionals. During the last decade, scientists have (a) created diagnostic criteria for CFS, (b) devised CFS assessment approaches, (c) collected CFS epidemiological data, and (d) formulated CFS treatment approaches. The CFS diagnostic criteria identify a subpopulation of individuals with this disorder, and those individuals might have a greater tendency to have psychiatric comorbidity. In addition, the initial CFS epidemiological data collected might have underestimated the prevalence of this disorder. If current estimated prevalence rates of CFS are inaccurate, these estimates could have detrimental public policy implications. Health care professionals need to assume a larger role in defining this syndrome, in developing more sensitive research strategies for collecting data with CFS samples, in conceptualizing more complex theories for understanding this disease, in conducting more rigorous CFS epidemiological research, and in devising more comprehensive treatment approaches for CFS.