ISO/TS 25237:2008 contains principles and requirements for privacy protection using pseudonymization services for the protection of personal health information. ISO/TS 25237:2008 is applicable to organizations who make a claim of trustworthiness for operations engaged in pseudonymization services. ISO/TS 25237:2008: defines one basic concept for pseudonymization; gives an overview of different use cases for pseudonymization that can be both reversible and irreversible; defines one basic methodology for pseudonymization services including organizational as well as technical aspects; gives a guide to risk assessment for re-identification; specifies a policy framework and minimal requirements for trustworthy practices for the operations of a pseudonymization service; specifies a policy framework and minimal requirements for controlled re-identification; specifies interfaces for the interoperability of services interfaces.