This evening I propose to offer you some of the results of my research for a book I have recently completed. I examined the work of canonists, in the Eastern and Western parts of the Christian community. I explained what they did and indicated the contribution they made to the development of canon law in the first millennium of Christianity. The book deals primarily with Rome and Constantinople, though there is an excursus into Methodius and the Slavs and into the Churches in Syria and Persia. What binds the chapters together, and makes them more than a collection of disparate essays, is the parallel discussion of three issues. These are: the constitution and governance of the Church (monarchical, patriarchal/imperial, synodal), the discipline of the clergy (married or celibate) and the question of re-marriage in church after divorce