Statin is one of the most commonly prescribed medicines in the developed World. In 2016, statin was the most commonly prescribed medicine in the UK. An original investigation by The Journal of the American Medical Association Cardiology (JAMA Cardiology) - one of American most prestigious peer-reviewed medical journals found that statin use among American adults 40 years of age and older has increased 79.8% in 10 years; i.e. from 17.9% in 2002-2003 to 27.8% in 2012-2013. On the contrary, the 2016 update of guidelines issued by the European Society of Cardiology (ESC), is persistent with a threshold of a 5% risk of fatal cardiovascular disease in 10 years. At the August ESC conference, cardiologists stated that lifestyle, nutrition, body mass index and weight are the major focus of the new guidelines. Despite being one of the mainstay treatments of atherosclerotic cardiovascular diseases (ASCVD), statin is still in the middle of this decades-long debate. In the midst of these controversies, this thesis attempts to provide a general review of the effectiveness of statin therapy in the management of ASCVD.