UMIN-CTR has changed prefix of the unique registration number since Aug 1 2006.

The new registration number is started with "UMIN" followed by nine-digit numeric number (e.g. UMIN123456789). A structure of the nine-digit numeric number was not rest so that you can search clinical trials with nine-digit number for the search. You can enter only numeric number, such as "000056789" to search registration numbers with either old ("C") or new ("UMIN") prefix.