The International Classification of Diseases, Tenth Revision (ICD-10) is the newest version of the common tool used to turn diagnoses and procedures into a universally recognized machine-readable sequence. It replaces the decades-old ICD-9 code standard. It has greater complexity, because it identifies twice as many diagnostic codes as ICD-9, 20 times as many injuries and 50 times as many procedures. Moreover, ICD-10 allows for alphanumeric codes and modernizes the fundamental structure for code assignment now and in future releases. ICD-10 is used almost exclusively in the U.S., although its use will not become mandatory until 1 October 2013. Implementation of the U.S. Health Insurance Portability and Accountability Act (HIPAA) X12, version 5010 standard is a prerequisite for using ICD-10. This standard will become mandatory on 1 January 2012.Implementation of HIPAA 5010 is largely a technical electronic data interchange similar to a version control of an application. ICD-10 is much more complex because it changes IT and business operation attributes. Correctly implemented, it will increase coding accuracy and improve the care management, reimbursement and rating processes. In the short term, however, it is expensive and difficult to implement because of the many processes and applications affected by coding changes. It will also cut claims-processing auto-adjudication rates.