The key mission of the Psychosocial Assessment Core is to generate a comprehensive set of information about the psychosocial and behavioral changes that occur as a result of the interventions proposed for this Chronic Fatigue Syndrome (CFS) Research Center. This Core is responsible for conducting a basic phone screen to rule out individuals who do not meet essential criteria, scheduling screening visits for prospective recruits, conducting face-to-face psychiatric screening interviews, administering psychosocial questionnaires at each time point in each of the Center's studies, ensuring participants' comfort and minimizing participant burden, and coordinating participant compensations. The administration of these measures by a central core is reasonable given that (a) all of these measures will be utilized in each project of this Center, and (b) administration of measures by Core personnel would provide the constancy of assessment conditions and blinding of participants' group assignment needed in order to conduct unbiased Center-wide comparisons. At the same time such a blinded procedure may allow participants to respond to certain questions (e.g., concerning health behaviors) honestly without fear of offending study personnel with whom they may have bonded (e.g., intervention group leaders) over the course of the study. The Psychosocial Assessment Core personnel will work with the other Cores to assure the appropriate placement of specific participants into the different projects and to ensure completion of assessments at each time point for all of the projects.