DICOM PS3.5 2024b - Data Structures and Encoding

7.2 Group Length

Group Length (gggg,0000) Data Elements were implicitly defined for Standard and Private Data Element groups with a Value Representation of UL and a Value Multiplicity of 1, but have been retired. See PS3.5-2007.

All implementations shall be able to parse Group Length Data Elements, and may discard and not insert or re-insert them; if present they shall be consistent with the encoding of the Data Set even if the Transfer Syntax is changed resulting in a change in the actual length of a group of Data Elements. No implementation shall require the presence of Group Length Data Elements.


  1. Elements in groups 0, 2, 4 and 6 are not Standard Data Elements. Mandatory requirements for Group Length for groups 0 and 2 are specified elsewhere in the Standard.

  2. It is recommended that Group Length Data Elements be removed during storage or transfer in order to avoid the risk of inconsistencies arising during coercion of Data Element Values and changes in Transfer Syntax.

DICOM PS3.5 2024b - Data Structures and Encoding