The International Association for Research on Cancer (IARC) and the World Health Organization (WHO) approved additions, changes, and revisions to the International Classification of Diseases for Oncology, Third Edition (ICD-O-3) on September 1, 2011. The purpose of the ICD-O-3 Implementation workgroup is to define steps for implementation of the ICD-O-3 revisions, including an implementation date, and create an implementation guide.