Circulating counterfeit medicines in the market is a public health threat. Counterfeit medicines become common problem, not only in developing countries, but also in industrialised countries, as internet has made them more accessible. In Japan, the recent survey on the medicines purchased through on-line pharmacy (targeting Japanese consumers) showed that the majority of erectile dysfunction (ED) medicines imported by individuals in Japan were counterfeit version. The survey of Japanese consumers, who privately imported medicines through on-line pharmacy, indicated that 16% of these consumers experienced adverse events associated with these products. Not only that it is just fake brand, but fake medicines may even cause health hazard. The counterfeit version of Avastin recently detected in the United States became a serious threat for those who desperately need these medicines for life-threatening disease. The Japanese regulatory authorities have provided risk information of counterfeit medicines to general public, as well as monitored on-line pharmacies and conducted enforcement action where necessary. However, more resources of compliance activity should be allocated to respond to the situation of growing threats of counterfeit medicines. Purchasing medicines from abroad through unauthorised channel is the major source of counterfeit medicines. It is essential to prevent circulation of counterfeit medicines through international collaboration of various regulatory authorities. To address these problems, the World Health Organization (WHO) has launched a new Member States Mechanism (MSM) to build network of the authorities. Also, INTERPOL (ICPO) initiated globally concerted enforcement actions (Operation Pangea) against pharmaceutical crime as well as built partnership with pharmaceutical industry to create Pharmaceutical Crime Programme. It is also necessary to prevent consumers encountering counterfeit medicines and to prevent health hazard. The Ministry of Health, Labour and Welfare (MHLW) has been actively involved in prevention and educational activities such as public awareness campaign. MHLW started anti-counterfeit medicines and new psychoactive substance project from February 2013, which centrally collects information about counterfeit medicines, in particular, and provides the risk information more effectively to the public. Japanese Government will work together with international community and contribute to combating counterfeiting through public and private partnership.