Link to this article: http://journals.cambridge.org/abstract_S0143385707000405 How to cite this article: YONGXIA HUA, RADU SAGHIN and ZHIHONG XIA (2008). Topological entropy and partially hyperbolic diffeomorphisms.Abstract. We consider partially hyperbolic diffeomorphisms on compact manifolds. We define the notion of the unstable and stable foliations stably carrying some unique nontrivial homologies. Under this topological assumption, we prove the following two results: if the center foliation is one-dimensional, then the topological entropy is locally a constant; and if the center foliation is two-dimensional, then the topological entropy is continuous on the set of all C ∞ diffeomorphisms. The proof uses a topological invariant we introduced, Yomdin's theorem on upper semi-continuity, Katok's theorem on lower semi-continuity for two-dimensional systems, and a refined Pesin-Ruelle inequality we proved for partially hyperbolic diffeomorphisms.