The adverse events which do not appear in the approval process tend to occur more frequently at the early stage of the use. Therefore new drugs, drugs with different active substances or routes of administration, or drugs with explicitly different efficacy added are particularly chosen for re-examination, and go through a study, which is conducted on 600 to 3,000 subjects over 4 to 6 years. Since the re-examination system was implemented in January 1995, 880 drug products have been designated as the subject of re-examination and among them 194 drugs have been completed their re-examination as of until March 2005. Post Marketing Surveillance to insure drug safety should be correlated with re-examination of new drug, re-evaluation of drug, and adverse event monitoring system. And the first labeling change should reflect all information collected for a defined period of time after the marketing authorization is granted. Furthermore centralized management through spontaneous reporting system of adverse event for whole period of time would be the most desirable type of system.