This volume is the fruit of an instructional conference on algebraic number theory, held from September 1st to September 17th, 1965, in the University of Sussex, Brighton. It was organized by the London Mathematical Society under the auspices and with the generous financial aid of the International Mathematical Union and of the Advanced Study Programme of "NATO The organizers of the conference owe a great deal to the constant support which they received from the authorities of the host University.