Testosterone prescriptions for men have risen sharply recently, particularly in North America. Observationally low testosterone among men is associated with a higher risk of cardiovascular disease. In two different studies testosterone prescription has unexpectedly been observed associated with a higher risk of cardiovascular events. The safety of testosterone is now being reviewed by the Food and Drug Administration in the U.S., by Health Canada and by The European Medicines Agency in Europe. To inform this debate a researcher from the City University of New York, independent of the pharmaceutical industry, has summarized all the evidence concerning the role of testosterone in cardiovascular disease and its risk factors focusing on evidence from randomized controlled trials, Mendelian randomization and mechanistic experiments. Taken together these studies do not confirm the benefits of testosterone seen in observational studies, but instead suggest testosterone administration causes cardiovascular-related events via biologically plausible mechanistic pathways involving raising hematocrit, lowering HDL-cholesterol, and increasing coagulability.