Abstract: A time-temperature indicator device for recording the duration of time over which a temperature has been established above a predetermined temperature, which device includes a dye-compatible polymer composition having a softening point above the predetermined temperature and a polymer-compatible dye composition in contact with the polymer composition and present in a quantity with respect to the polymer composition sufficient for diffusion through the polymer composition whenever the polymer composition is above the predetermined temperature, which quantity is selected so that the extent of diffusion corresponds to the duration of exposure above the predetermined temperature relative to the total time required for substantially complete diffusion. Articles for which a heat history above a predetermined temperature is to be record, in combination with the disclosed time-temperature indicator devices are also described.