The USMARC classification format, developed in the early 1990s for the DDC and LCC systems, is also amenable for other classification systems. This paper presents a proposal for using the MARC classification format for UDC. There are advantages in using this format for the UDC data in an authority file, e.g., for the MRF records and records for combined notations as well. There has been a trend in library catalogues for subject interoperability between traditional classification systems such as the UDC, DDC, LCC and subject headings. An example with great impact is WebDewey, which offers interlinking between classification numbers, the alphabetical index of the tables and LCSH. Another example is the electronic version of LCC Plus, also including links to LCSH. Subject gateways built upon library authority files can support the interoperability between classification systems and subject headings. These gateways can be the backbone of a more universal access through hypertextual navigation structures supported by classification systems including UDC. To our knowledge, the MARC classification format has not yet been applied to the UDC and in this paper we are going to propose a solution supported by some examples.