This study of the theory of electrical and thermal conduction in metals, semiconductors, and insulators is written at a level appropriate to graduate students and research workers and assumes some knowledge of wave mechanics in its reader. The basic ideas of crystal lattice dynamics, electron zone structure, and transport theory are developed from first principles, and formulae for the macroscopic coefficients are deduced by self-contained mathematical arguments. Interpretation in terms of electronic structure, chemical purity, crystal structure, and crystal perfection is emphasized as a tool for further investigation but detailed discussion of individual means or alloys is avoided.