See also corresponding RFC for X500 / LDAP Internet implementation, x500 discussion, and X509 certificates standards

X500 is a set of OSI standards maintained by ITU (X501 to X586). It concerns Directory systems. ISO maintains the standard under its own numbering (ISO/IEC 9594 part 1, to part 8)

X500 set and table of content and implementation guide from ITU version 1, ITU version 2 or ISO

Information technology - Open Systems Interconnection - The Directory: Models. (ISO/IEC 9594-1-1998, FDIS9594-1, 9594-1-2001,for concepts and services, 9594-2-1998, FDIS9594-2, 9594-2-2001 for model)

X501 Abstract, and release notes

Information technology - Open Systems Interconnection - The Directory: Public-key and attribute certificate frameworks. This is the most successful part of X500 standards, and as such several ISO/IEC subsets are described and under work, refer to X509 page for more .  

Information technology - Open Systems Interconnection - The Directory: Abstract service definition.

X511 Abstract.

IInformation technology - Open Systems Interconnection - The Directory: Procedures for distributed operation, (ISO/IEC 10021-4).

Information technology - Open Systems Interconnection - The Directory: Protocol specifications

Information technology - Open Systems Interconnection - The Directory: Selected attribute types , (ISO/IEC 10021-5)

Information technology - Open Systems Interconnection - The Directory: Selected object classes, (ISO/IEC 10021-6)

Information technology - Open Systems Interconnection - The Directory: Replication, (ISO/IEC 10021-7)

Information technology - Open Systems Interconnection - The Directory: Use of systems management for administration of the Directory

Information technology - Open Systems Interconnection - The Directory: Protocol Implementation Conformance Statement (PICS) proforma for the Directory Access Protocol, (ISO/IEC 10021-8 and 10021-9), see also ISO EDIseries 9735, 12073, 14662, and 15944.

Information technology - Open Systems Interconnection - The Directory: Protocol Implementation Conformance Statement (PICS) proforma for the Directory System Protocol

Information technology - Open Systems Interconnection - The Directory: Protocol Implementation Conformance Statement (PICS) proforma for the Directory Operational Binding Management Protoco.

Information technology - Open Systems Interconnection - The Directory: Protocol Implementation Conformance Statement (PICS) proforma for the Directory Information Shadowing Protocol