This paper describes existing International Standards Organization (ISO) standards and current activity concerned with thermal comfort. It describes how an ISO standard is produced from a new work item proposal to publication as an International Standard. ISO Standards should be valid, reliable, useable, and with sufficient scope for practical application. The existing thermal comfort standard-EN ISO 7730-is considered in terms of these criteria as well as ISO 8996 (metabolic rate) and ISO 9920 (clothing). The work of ISO/TC 159 SC5, 'ergonomics of the physical environment', is presented in Appendix A. The proposed revision of EN ISO 7730 is presented in detail. The revised standard will be based on requirements for general thermal comfort (predicted mean vote (PMV), operative temperature) and local thermal discomfort (radiant temperature asymmetry, draught, vertical air temperature differences, floor surface temperatures). One critical issue is the effect of air velocity. Increased air velocity has a beneficial effect at warm temperatures, but it may result in draught sensation in cooler temperatures. Another issue is the extent to which requirements of humidity need to be included in a standard for thermal comfort. Several recent research projects dealing with adaptation, influence of air velocity and the effect of humidity have been responsible for keeping the standards up to date.