Most papers published in this volume are based on lectures presented at the Chico Conference on Semigroups held on the Chico campus of the Cal- ifornia State University on April 10-12, 1986. The conference was spon- sored by the California State University, Chico in cooperation with the Engineering Computer Sciences Department of the Pacific Gas and Electric Company. The program included seven 50-minute addresses and seventeen 30-minute lectures. Speakers were invited by the organizing committee consisting of S. M. Goberstein and P. M. Higgins. The purpose of the conference was to bring...