Abstract It is unclear which psychological and biological variables are potential maintenance factors for ME/CFS following IM because few prospective studies have collected baseline data before the onset of IM and then followed these subjects prospectively following the diagnosis of ME/CFS. In our currently funded NIH study, the focus has been on pre-illness clinical and biological predictors of ME/CFS development following IM in a diverse group of college students. General screens of health and psychological well-being, as well as blood, were obtained at all three stages of the study (Stage 1 - when the students are well; Stage 2 – at the time they are acutely ill with IM, Stage 3 – six months after IM, when they have either developed ME/CFS or recovered). Wave 1 refers to data we are currently collecting and Wave 2 will be funded by the proposed grant and involves a five-year follow-up with the original Wave 1 subjects. Cohort 1 includes those college students who developed IM during Wave 1, and preliminary data indicate that these students showed marked differences at baseline from those who did not develop ME/CFS 6 months following IM. Cohort 2 includes those who did not develop IM in Wave 1. We expect some of these subjects will develop ME/CFS over time. Our study will assess both clinical and biological maintenance factors for of ME/CFS following IM, and determine prospectively the incidence of ME/CFS in a sample of young adults.