Chiral perturbation theory for hadrons containing a heavy quark

An effective Lagrangian that describes the low-momentum interactions of mesons containing a heavy quark with the pseudo Goldstone bosons π, K, and η is constructed. It is invariant under both heavy-quark spin symmetry and chiral SU(3)L×SU(3)R symmetry. Implications for semileptonic B and D decays are discussed.