Since its beginning in 1969 the British Combinatorial Conference has grown into an established international meeting. This year the twelfth conference is being held in Norwich under the auspices of the School of Mathematics at the University of East Anglia. Participants come from a great number of countries worldwide and represent a multitude of interests in combinatorial theory.

This volume contains the contributions of the principal speakers. They were invited to prepare a survey paper for this book and to deliver a lecture in an area of their expertise. In this way it is hoped to make available a valuable source of reference to the current state of art in combinatorics. The speakers have produced their papers well in advance so that they are now all available in time for the conference.

This book has been produced to a tight schedule. I am grateful to the authors for their cooperation and to the referees for their assistance and comments about the papers. The British Combinatorial Conference is largely selffinancing but on behalf of the committee I would like to thank the London Mathematical Society, Norwich Union and Peat Marwick McLintock for their financial support.