It is possible to migrate from antecedent versions to SNOMED CT. The International Release of SNOMED CT includes migration tables between antecedent versions and SNOMED CT. Furthermore, a number of additional maps are available from country National Release Centers. Maps available internationally include a SNOMED II to SNOMED RT bridge file and a SNOMED 3.5 to SNOMED RT bridge file. (All SNOMED RT codes ended up in SNOMED CT, so these bridge files are from legacy codes to SNOMED CT as it was in 2002. The map from legacy codes that were produced after SNOMED CT was first produced are already in SNOMED CT.)

For further information about mapping from antecedent versions to SNOMED CT, please see the information sheet at the bottom of the following webpage: