INTERNATIONAL CONFERENCE ON HARMONISATION OF TECHNICAL REQUIREMENTS FOR REGISTRATION OF PHARMACEUTICALS FOR HUMAN USEICH HARMONISED TRIPARTITE GUIDELINEIMPURITIES IN NEW DRUG SUBSTANCESQ3A(R2)Current Step 4 versiondated 25 October 2006This Guideline has been developed by the appropriate ICH Expert Working Group and has been subject to consultation by the regulatory parties, in accordance with the ICH Process. At Step 4 of the Process the final draft is recommended for adoption to the regulatory bodies of the European Union, Japan and USA.Q3A(R2)Document HistoryFirst CodificationHistoryDateNew CodificationNovember 2005Q3Approval by the Steering Committee under Step 2 and release for public consultation.15March 1994Q3AQ3AApproval by the Steering Committee under Step 4 and recommendation for adoption to the three ICH regulatory bodies.Q3 was renamed Q3A.30March 1995Q3AQ3A(R)Approval by the Steering Committee of the first Revision under Step 2 and release for public consultation.7October 1999Q3A(R1)Q3A(R)Approval by the Steering Committee of the first Revision under Step 4 and recommendation for adoption to the three ICH regulatory bodies.6 February 2002Q3A(R1)Current Step 4 versionQ3A(R2)Approval by the Steering Committee of the revision of the Attachment 2 directly under Step 4 without further public consultation.25 October 2006Q3A(R2)IMPURITIES IN NEW DRUG SUBSTANCESICH Harmonised Tripartite GuidelineHaving reached Step 4 of the ICH Process at the ICH Steering Committee meeting on 7 February 2002, this guideline is recommended for adoption to the three regulatory parties to ICH.Attachment 2 has been revised on 25 October 2006.TABLE OF CONTENTS1.PREAMBLE..............................................................................................