The rates of isothermal nucleation and growth in chalcogenide glass thin films of (GeS2)(0.9)(Sb2S3)(0.1) were studied using optical microscopy. Nucleation data was obtained from double stage heat treatment, followed by image analysis of polarized optical micrographs. The applicability of classical nucleation theory (CNT) to the nucleation data has been discussed. The growth data, corrected for viscosity suggest interface controlled 2D nucleated growth of beta-GeS2 crystals. The isothermal curves of nucleation and growth determined by CNT and 2D nucleated growth model, respectively were found to be weakly intersecting. The nucleation curve had maxima at 350 degrees C, which is below the glass transition temperature, while the growth curve had a peak at 439 degrees C. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.