This study will be a prospective, double-blind, randomized, placebo-controlled, equal parallel groups study conducted at up to fifteen (15) centers to compare the safety and efficacy of Ampligen® IV versus placebo IV in 230-240 patients with CFS/ME. Patients will be randomized and stratified to receive either Ampligen® intravenously or placebo (normal saline) intravenously. Fifty percent (50%) of the patients will be treated with Ampligen® IV and 50% of the patients will be treated with placebo IV.