The efficacy of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) for reducing cardiovascular events has been established in large-scaled randomized controlled trials (RCT), and these trials have encompassed both primary and secondary prevention. Also, the safety of statins has been confirmed. Therefore, the market for statins is growing quite rapidly. Despite their proven benefits, a large number of patients who meet the guideline criteria for statin therapy are not receiving these drugs. Various strategies have been used to increase statin therapy in the target populations. However, the number of eligible patients taking statins has remained disappointing. It has been suggested that over-the-counter availability of statins would allow more consumers to use statins and achieve cardiovascular risk reduction. In contrast, those clinical trials have applied selection criteria to protect the internal validity at the expense of reducing the applicability of the trial's findings to the wider population of patients seen in routine clinical practice. Consequently, patients who are prescribed statins in routine clinical practice may systematically differ from those people who received statins in the clinical trials and may have different outcomes from those reported in the trials. This paper will review the efficacy of statins for preventing cardiovascular diseases, and suggest the pitfalls of the randomized controlled trails and the problems in the prescription of statins in the real clinical practice.