Statin drugs are widely prescribed to achieve aggressive low-density lipoprotein lowering in order to decrease cardiovascular disease. Although some of the immunomodulatory effects of statins may stabilize atherosclerotic plaque, they may be harmful in certain segments of the population. Recently, statins have been shown to increase the concentration of regulatory T cells (Tregs), in vivo. There is evidence that this increases the risk of many cancers, particularly in the elderly. Furthermore, a statin induced increase in Tregs may be detrimental in neurodegenerative disorders, such as amyotrophic lateral sclerosis; and a myriad of infectious diseases. These include, but are not limited to, human immunodeficiency virus, hepatitis B virus, hepatitis C virus, and varicella zoster virus. These issues need our attention, and call for a heightened state of vigilance among those prescribing statins.