Over 40 years, Post-maketing surveillance (PMS) studies have been conducted as a legal obligation in Japan. Though the contribution of these studies to the better use of the drug has been acknowledged, there are criticisms that these PMS studies have been stereotyped and need to be improved. The ICH-E2E guideline entitled as "Pharmcovigilance Planning", agreed in the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) has been implemented in the concerned countries. The legislation of the guideline in Japan in 2005 seems to have urged drug companies and regulatory agency to review the current PMS practices in contrast with the today's highest scientific standard. We investigated the theoretical and practical aspects of pharmacoepidemiology required when the drug company evaluates safety specification prior to developing the pharmacovigilance plan and designs a PMS study along the lines stipulated in the ICH-E2E guideline. To meet this end, we evaluated the profiles of the drug, summarized "Important identified risks", "Important potential risks" and "Important missing information" to be identified and examined the pharmacovigilance plan suggested by the regulatory agency and that proposed and implemented by the drug company. We examined those aspects for 6 new products selected from 168 drugs newly approved during the period between January 2004 and October 2006. In 5 of 6 cases, we judged that the use of a comparator group would have been appropriate to asses the association between the drug and adverse events of interest. In addition, in one half (3) of 6 cases, it would have been preferable to use the database for the patient registration and/or other types of databases. The issues of relevant legislation and the infrastructure and funding for the investigations needed to develop a desirable study design and conduct a good pharmacoepidemiology study are however beyond a single company's capacity and should be set as a national strategy. The issues of post-marketing safety in the nation is becoming more and more important as the data in the countries outside Japan are being used more often for the processes of marketing authorization application of a new drug and its approval. It is urgent to secure the practice of pharmacoepidemiology to achieve the effective post-approval pharmacovigilance studies.