| ADMD | Administration Management Domain |
| AJPO | Ada Joint Program Office |
| ANSI | American National Standards Institute |
| AOW | Asia-Oceania Workshop |
| API | Application Program Interface |
| APIA | API Association |
| APPC | Advanced Peer-to-Peer Communication |
| ASCII | American National Standard Code for Information Interchange |
| ATS | Abstract Test Suite |
| BSFT | Byte Stream File Transfer |
| BSI | British Standard Institution |
| CAE | Common Application Environment |
| CCTA | Government Center for Information Systems |
| CEN | Comité Européen de Normalisation (European Committee for Standardization) |
| CENELEC | Comité Européen de Normalisation ELECtrotechnique (European Committee for Electrotechnical Standardization) |
| CEPT | European Confederation of Postal and Telecommunications Administrations |
| CLNS | Connectionless-mode Network Service |
| CMIP | Common Management Information Protocol |
| CMIS | Common Management Information Service |
| CONS | Connection-mode Network Service |
| COS | Corporation for Open System |
| CPI-C | Common Programming Interface for Communication |
| CRAMM | CCTA Risk Analysis and Management Methodology |
| CSMA/CD | Carrier Sense Multiple Access / Collision Detection |
| CSQ | Conformance Statement Questionnaire |
| CTS | Conformance Testing Services |
| DIB | Directory Information Base (X.500) |
| DIR | Directory Services |
| DIS | Draft International Standard |
| DIT | Directory Information Tree (X.500) |
| DNI | Detailed Network Interface |
| DSA | Directory Service Agent (X.500) |
| DSP | Directory System Protocol |
| DUA | Directory User Agent (X.500) |
| DUA | Directory Access Protocol |
| EBCDIC | Extended Binary Coded Decimal Interchange Code |
| ECITC | European Committee for IT Testing and Certification |
| EDI | Electronic Data Interchange |
| EDIFACT | EDI for Administration, Commerce and Transport (UN/ISO) |
| EDIM | EDI Messaging |
| EN | European Norm |
| ENV | European Pre-norm (Vornorm) |
| EPHOS | European Procurement Handbook for Open Systems |
| ESTELLE | Extended Finite State Machine Specification Language |
| ETCOM | European Testing and Certification for Office and Manufacturing |
| ETSI | European Telecommunications Standard Institute |
| EWOS | European Workshop for Open Systems |
| FDDI | Fibre Distributed Data Interface |
| FTAM | File Transfer, Access and Management (ISO) |
| FTP | File Transfer Protocol |
| GKS | Graphical Kernel System |
| GOPIP | Government Open Systems Interconnection Profile |
| INTAP | Interoperability Technology Association for Information Processing |
| IPM | Interpersonal Messaging (X.400) |
| IS | International Standard |
| ISAM | Indexed Sequential Access Method |
| ISDN | Integrated Services Digital Network |
| ISP | International Standardized Profile |
| IT | Information Technology |
| IUT | Implementation Under Test |
| LAN | Local Area Network |
| LLC | Logical Link Control |
| LOTOS | Language of Temposal Ordering Specification |
| LU | Logical Unit |
| MHS | Message Handling System (X.400) |
| MOTIS | Message-Oriented Text Interchange System |
| MS | Message Store |
| MTA | Message Transfer Agent (X.400) |
| MTS | Message Transfer System (X.400) |
| NAMAS | National Measurement Accreditation Scheme |
| NBS | National Bureau of Standards |
| NCC | National Computer Center |
| NFS | Network File System |
| NIST | National Institute of Standards and Technology |
| NLM | Network Lock Monitor |
| NSM | Network Status Monitor |
| ODA | Open (Office) Document Architecture (ISO) |
| OIW | OSI Implementors Workshop (VT) |
| OMG | Object Management Group |
| OSI | Open System Interconnection |
| OSTC | Open System Testing Consortium |
| PCTR | Protocol Conformance Test Report |
| PHIGS | Programmer's Hierarchical Interactive Graphics System |
| PICS | Protocol Implementation Conformance |
| PIXIT | Protocol Implementation eXtra Information for Testing |
| POSIX | Portable Operating System Interface |
| PRMD | Private Management Domain |
| PSI | Process to Support Interoperabiity |
| PSTN | Public Switched Telephone Network |
| RPC | Remote Procedure Call |
| SAA | System Application Architecture |
| SCTR | System Conformance Test Report |
| SDL | Specification and Description Language |
| SMB | Service Message Block |
| SNA | System Network Architecture (IBM) |
| SNI | Simple Network Interface |
| SPAG | Standard Promotion and Application Group |
| SQL | Structured Query Language |
| SUT | System Under Test |
| SVC | Switched Virtual Circuit |
| TC | Technical Committee |
| TCP/IP | Transmission Control Protocol / Internet Protocol |
| TFA | Transparent File Access |
| TLFF | Technical Level Feeders Forum |
| TMLA | Trade Mark Licence Agreement |
| TP | Transaction Processing |
| UA | User Agent (X.400) |
| UDP | User Datagram Protocol |
| UN | United Nations |
| VT | Virtual Terminal (ISO) |
| WAN | Wide Area Network |
| XTI | X/Open Transport Interface |