Smart textiles are materials andstructure that sense and react to environmental conditions or stimuli, such asthose from mechanical, thermal, chemical, electrical, magnetic or othersources. The Phase Change Materials are those which change their phase fromsolid to liquid upon heating and back to solid from liquid when temperature isdrop down. During their phase change from Solid to liquid they absorb,distribute and store the heat, and release it when going a phase change fromliquid to solid. Thus it keeps the wearer skins temperature constant byabsorbing the excess heat and releasing it when required. PCM possesses theability to change their phase with a certain temperature range, which can becontrolled by choosing the various phase change material according to the enduse of the product. This paper discuss about the principle of Phase ChangeMaterial, Its different type available. The different technology used for theincorporation of phase change materials into textile substrate and their applicationwith limitation is been discussed.