A three-dimensional cellular automaton (CA) model is applied to simulate isothermal crystallization of monomer casting (MC) nylon 6. The kinetics is formulated based on the Kim and Kim's rate theory for spherulite expansion. The probability of distribution of crystalline nuclei and impinging were determined by Monte Carlo method. The spherulite impinging was considered in the simulation through the deduction of overlay of spherulite volume. The number of spherulite nuclei and bulk density of MC nylon 6 after completing crystallization, easily obtained from experiment, were used as input data, allowing one to make predictions on a real time and space scale. Finally, the model was verified by quantitative comparison between the simulation results in this work and experimental data in literatures. (C) 2008 Elsevier Ltd. All rights reserved.