This is a primer in jazz theory, intended to prepare the student for the serious study of jazz improvisation, arrangement and composition. The focus is on the harmonic language of jazz, especially the harmonic practices which coalesced in the bebop and post bop periods of the 1940s and 1950s when bebop and standard tunes formed the core of the mainstream repertoire. The harmonic language of that period is still the framework on which contemporary jazz musicians build. Included are many musical examples and written assignments for practice in the theoretical skills. Appropriate exercises are provided to reinforce theoretical concepts by immediate application to the instrument.