Previous models of the Zener pinning of migrating grain boundaries by precipitates are all based on spherical or ellipsoidal particles. In this work, theoretical and experimental studies are made of pinning by stable, cubic-shaped particles. It is shown that cubic-shaped particles are generally more effective than spherical particles in holding up grain growth. Pinning is also more effective if particles are fully coherent. Transmission electron microscopy is used to study actual grain boundary/particle interactions in a Ti-microalloyed steel in which the coherent precipitate is a stable, cubic-shaped titanium nitride compound. The interactions observed are discussed in the light of the models developed