The present natural history study examined the course of CFS from 1995-97 (Wave 1) to approximately 10 years later (Wave 2) from a random, community-based, multi-ethnic population. The rate of CFS remained approximately the same over the period of time from Wave 1 to Wave 2, although a high level of mortality was found (18% of those with medical or psychiatric exclusions group, 12.5% for the CFS group). Physical measures of disability and fatigue, along with measures of specific somatic symptoms, better differentiate individuals who later are diagnosed with CFS than more psychosocial measures such as stress and coping.