Thermal and optical properties of unirradiated and g-irradiated polyester track detector films in the dose range of 0-14.5 Mrad have been studied by thermogravimetry (TG) and UV-Visible spectroscopic technique. The samples were irradiated with ⁶⁰Co g-rays for doses of 4.7, 8.1 and 14.5 Mrad. The TG studies indicate that unirradiated and the g-irradiated samples degrade in two steps. The kinetics of the two steps of degradation were also evaluated from the TG curves. Irradiation enhances the degradation rate and the effect increases further with increasing radiation dose. The optical band gaps of the unirradiated as well as the irradiated samples were also determined from the UV-Visible spectra. These studies can be used for the estimation of g-dose using changes in absorbance and the activation energy due to g -irradiation.