The process for a new drug approval in Korea is very similar to that in the United States. Pharmaceutical company should submit all the relevant data on the safety and efficacy of the potential new drug including preclinical experimental data and clinical trial data. The re-examination system for new drugs has been effective since Jan 1, 1995. According to the guideline, pharmaceutical company should submit the predetermined number of safety data on the new drug after 4 or 6 years since it was approved to be marketed from the government. The purpose of this paper is mainly for explaining the concept and methods for effective conduction of the re-examination process. And the secondary purpose is to suggest the need and possible solutions for developing more proper drug safety evaluation system in Korea.