Computer simulations have been developed to investigate the intramolecular cyclization of polyimides (i.e., imidization, the conversion of the precursor polyamic acid into polyimide). Imidization was examined as a function of time, temperature, and presence or absence of a silica substrate. To do this, the essential results of quantum mechanical studies were incorporated into a molecular dynamics simulation. Molecular dynamics simulations were used to determine the conformational properties of the polymer chain and to simulate the imidization reaction when the conformational criteria established by quantum mechanical methods were met. In agreement with experiments, imidization occurred in two distinct stages, and increased temperatures were shown to produce higher extents of imidization. Finally, the interfacial chains exhibited more complete imidization than the isolated chains. These results not only support the proposed molecular rationale behind the kinetic models of imidization but also demonstrate that only local chain motions are necessary for imidization to occur.