A phase field model is presented for simulating grain growth in materials containing small incoherent second-phase particles that are constant in time. The model of [L.-Q. Chen, W. Yang, Phys. Rev. B 50 (1994) 15752] for grain growth in single phase materials, that represents a polycrystalline microstructure with a set of phase field variables eta(i)(r,t), has been modified to incorporate the presence of second-phase particles by adding an extra term epsilon Phi Sigma(i)eta(i)(2) to the free energy expression, with Phi a spatially dependent parameter that equals one inside the particles, and zero elsewhere and Phi a positive constant. The interaction between a particle and a diffuse interphase is analyzed from an energetic point of view and the effect of pinning particles on the shape and the evolution of an initially spherical grain is studied for two-dimensional and three-dimensional systems. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.