The coherent-state transform is used in obtaining a global, uniform asymptotic solution of the wave equation. This solution approximates high-frequency propagation of acoustic, optical, and seismic waves in generally heterogeneous media. The coherent-state approximation has an advantage over more traditional methods, because it leads to a well-defined approximation independent of the complexity of the caustics. As illustrations, homogeneous media, focusing and edge diffraction are discussed. The homogeneous and waveguide solutions reduce to the exact solution; and the diffracted wave has the correct asymptotic form but the accuracy depends on a parameter. Numerical calculations demonstrate how the accuracy is influenced by variations of this parameter