The Revision Procedure is followed either in cases where the scientific/technical content of an existing ICH Guideline is no longer up-to-date or valid, or in cases where there is new information to be added with no amendments to the existing ICH Guideline necessary. In the case of the latter, the new information can be added in the form of an Addendum or an Annex to the Guideline in question.

The procedure is initiated with the endorsement by the ICH Assembly of a Concept Paper. For revisions a Business Plan is not necessary. An Expert Working Group (EWG) is subsequently established.

The Revision Procedure is almost identical to the Formal ICH Procedure i.e., 5 ICH Steps. The only difference is that the final outcome is a revised version of an existing Guideline, rather than a new Guideline.

The revision of a Guideline is designated by the letter R1 after the usual denomination of the Guideline. When a Guideline is revised more than once, the document will be named R2, R3, R4, etc… at each new revision. In cases where an Addendum or Annex has been developed, upon reaching Step 4 the Addendum or Annex is normally added to the existing Guideline resulting in a revised Guideline.