ISO standards are not numbered sequentially. They have a reference number composed of several descriptive fields. The first field defines the general heading under which a standard is indexed, for example: 01 = Generalities (terminology, standardization, documentation). 25 = Manufacturing engineering. 65 = Agriculture. This followed by a field that narrows the scope, for example: 31.040 = Electronics, resistors. 31.060 = Electronics, capacitors. 31.080 = Electronics, semiconductor devices. There may be more than one layer, for example: 45.060.10 = Railway engineeering, railway rolling stock, tractive stock. 45.060.60 = Railway engineeering, railway rolling stock, trailing stock. Following this is the specific standard number and the year in which it was adopted, for example: 45.080 = Railway engineering, rails and railway components. ISO 5003:1980 = Flat bottom railway rails and special rail sections for switches and crossings of non-treated steel - Technical delivery requirements. ISO 6305-2:1983 = Railway components - Technical delivery requirements - Part 2: Unalloyed carbon steel baseplates. Usually only the ISO listing is used as a reference (e.g., standards are generally referenced as ISO nnnn:yyyy), but it is only part of the larger indexing system. makes things easier to find. The first standard listed by family in the catalog is: 01.020 = Terminology, principles and co-ordination. ISO 704:2000 = Terminology work - Principles and methods. There is an ISO 1 standard, under: 17.040.01 = Metrology and measurements, linear and angular measurements, general. ISO 1:2002 = Geometrical Product Specifications (GPS) - Standard reference temperature for geometrical product specification and verification. You can search their catalog at: http://www.iso.org/iso/en/CatalogueListPage.CatalogueList Other standards bodies (e.g., IEC, ANSI, SAE) use different indexing system. None of them use the Dewey Decimal System. :-)