A great deal more is known today than 35 years ago about the underlying biology of ME/CFS. It is clear that many biological measurements clearly distinguish patients with ME/CFS from healthy control individuals. At the same time, some areas of ME/CFS research remain a challenge, and research has not yet given practicing physicians 2 important tools. First, there are as yet no US Food and Drug Administration – approved treatments. Second, although various biological measurements distinguish patients with ME/CFS from healthy controls, none yet have demonstrated the high sensitivity and specificity required for a good diagnostic test. However, 1 small study (20 cases and 20 controls) described at the NIH conference (and recently published) reported perfect sensitivity; the specificity of the test in individuals with other fatiguing illnesses remains to be shown. With growing international interest in the illness, and increased research support from the NIH, the day is coming when physicians will be able to explain to patients not only that there is something wrong but also that advances in understanding the pathophysiology have led to effective therapy.