In this work we study the Sobolev spaces generated by pseudo-di#erential operators associated with the group of symmetry of general first order hyperbolic systems. In these spaces we establish pointwise estimates of the solutions of a class of first order systems having convex eigenvalues. Various physical models belong to this class. For example, we consider crystal optics systems and anisotropic elasticity equations. Keywords. First order hyperbolic systems; Generalized Sobolev spaces; A priori estimates for wave type equations.