Viagra is a drug that has an effect on blood vessels and blood flow to certain areas of the body. It was originally developed as a potential treatment for hypertension and angina. It didn't turn out so useful for those things, but in the course of clinical trials, they discovered an interesting "side effect" which they decided was worth further investigation. Viagra (under another trade name) is used in treatment of pulmonary arterial hypertension (a relatrively rare condition), so it is good for some selected cardiovascular diseases. And Pfizer does continue to look at new uses, because believe it or not, the ED drug market has sort of leveled off - sales have not continued to increase after the initial excitement (heh heh) over the introduction of ED drugs. I'm a little stumped as to what "PTS" means in the above listing, but here is the full listing from clinicaltrials.gov about the study. http://clinicaltrials.gov/ct2/show/NCT00598585?recr=Open&cond="Fatigue Syndrome, Chronic"&rank=15 Seems like maybe a long shot, but not totally unfounded, I don't think it's worth getting incensed about. Look at the length of the study and the amount of funding - pocket change.