This paper is the first part of a theory of the coherent propagation of light in semiconductors. When the interaction between electrons is neglected we obtain the Bloch equation describing the matrix elements of interband transitions induced by coherent light in semiconductors. The interband transitions in the system are analogous in form to those of an inhomogeneously broadened two-level system, but a particular type of multiphoton process will occur under the action of intense light.