Fundamental models have been developed to describe swelling and dissolution of glassy polymer thin films. The models account for solvent penetration by either Fickian or Case II diffusion mechanims. The convective flux due to local swelling as the solvent penetrates is included. Chain disentanglement at the polymer-developer solution interface is scaled with the local solvent concentration and polymer molecular weight using reptation theory. The effective surface concentration during dissolution is estimated by applying thermodynamics of swollen networks to the entangled polymer. Swelling and dissolution of thin polymer films have direct application to microlithography. Various molecular and processing parameters affect the outcome of resist development. The utility of the models for selecting appropriate developer solvents, minimizing resist swelling, and providing a better understanding of the swelling and dissolution of resists is demonstrated.