Effects of high-dose neutron irradiation on chemical and optical properties of CR-39 were studied using FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) spectroscopy.The primary goal was to find a correlation between the neutron dose and the corresponding changes in the optical and chemical properties of CR-39 resulted from the neutron irradiation.The neutrons were produced by bombarding a thick Be target with 22-MeV protons.In the FTIR spectra,prominent absorbance peaks were observe dat 1735 cm^-1 (C=O stretching),1230 cm^-1(C–O–C stretching),and 783 cm^-1(=C–H bending),the intensities of which decreased with increasing neutron dose.The optical absorbance in the visible range increased linearly with the neutron dose. Empirical relations were established to estimate neutron doses from these optical properties.This technique is particularly useful in measuring high doses,where track analysis with anoptical microscope is difficult because of track overlapping.