Three-dimensional (3D) multi-phase field simulations are performed to study the lamellar stability of a directionally solidified hypereutectic CBr4-C2Cl6 alloy in both the longitudinal and the transverse directions. The 3D simulation results show that the morphology evolution in the longitudinal direction is consistent with that in two dimensions, but the morphology evolution in the transverse direction is much complex and some new patterns form. The discussion on the mechanism of lamellar spacing adjustment shows that the lamellar spacing adjustment in 3D is through lamellar termination and lamellar creation. (c) 2009 Elsevier B.V. All rights reserved.