Supplement to prospectus dated December 15, 2004 – OMX refi-nances subsidiaries and makes a provision for premises

OMX has earlier today published a press release with the following wording: “As a result of the proposed authorization for the Board of Directors of OMX to issue new shares in conjunction with the public offering to the shareholders of the Copenhagen Stock Exchange A/S, OMX has compiled a report on events of material importance to OMX’s financial position that have previously been announced via press releases. The report will be available at OMX from January 20, 2005 and will be distributed upon request to shareholders. In conjunction with the issuance of the report, OMX has decided to make a provision for premises and to refinance certain subsidiaries. Refinancing of subsidiaries The parent company will refinance certain subsidiaries as per December 31, 2004, at an amount of approximately SEK 630 million, due to accumulated deficits. OMX’s group results and total shareholders’ equity will not be affected by these measures, as the subsidiaries’ earlier deficits are included in the group’s shareholders’ equity brought forward and the year’s deficits are included in the year’s results. The parent company, OMX AB’s, results and share-holders’ equity will, however, be affected. The Board of Directors proposes that the resulting deficit in OMX AB shall be covered by utilization of restricted reserves. As a result of the refinancing and utilization of restricted reserves, the OMX group’s unrestricted reserves will increase, thereby improving future dividend capacity from 2005 and onwards. A deci-sion regarding the abovementioned utilization of restricted reserves will be made at the OMX An-nual General Meeting on April 7, 2005. Provision for premises During 2004, OMX has continued to focus on cost savings and streamlining of operations, resulting in a lower number of employees and, consequently, unused office space. The number of employees has decreased by more than 300 during 2004, which is more than was anticipated when launching the restructuring program in 2003. Due to weakened market conditions for subleasing, certain unuti-lized OMX office space has also been subleased at a lower rent than OMX’s contractual lease. As a result, OMX has decided to make a provision of SEK 130 million related to auxiliary premises. The auxiliary premises concern mainly OMX offices in New York and London. The provision will result in a negative effect on OMX’s operating income for the fourth quarter 2004. “ Please be aware that OMX’s offer to the shareholders of Copenhagen Stock Exchange expires on February 7, 2005. The completion of the offer is subject to certain conditions, including a minimum acceptance level of 90 percent. Shareholders wishing to tender their shares in Copenhagen Stock Exchange subject to the terms and conditions of the offer must contact their own account holding institution or stock brokerage company in this respect with a request for the acceptance of the offer to be communicated to Danske Bank A/S, Corporate Actions, Holmens Kanal 2-12, 1092 Copenha-gen K, Denmark, phone: +45 43 39 49 69 before the expiry of the offer period. This prospectus supplement is available on www.omxgroup.com and www.cse.dk. Furthermore the prospectus supplement will be send to all parties having received a copy of the prospectus. For more information, please contact: Anna Rasin, VP Marketing & Communications +46 8 405 66 12