Dr. Jose G. Montoya, Associate Professor of Medicine at Stanford, is conducting a study looking for pathogens that may be associated with Chronic Fatigue Syndrome. He is looking for patients with CFS who live in the San Francisco Bay Area to participate in the study. Participation in the study involves doing a20-minute phone screening interview. If you are eligible, you will be invited to have a60-minute study visit, including a blood draw. There is no cost to participate in the study. You will not receive any benefit from participation in this study, other than contributing to research. The results of the blood tests will be available to you within 12 months, but they are for research purposes only. If you are interested in participating or have any questions, please contact the study coordinator, Jane Norris, at (650) 723-8126. For general information about participant rights,contact 1-866-680-2906.