This volume contains the papers presented at the Ninth International Conference on Automated Deduction (CADE-9) held May 23-26 at Argonne National Laboratory, Argonne, Illinois. The conference commemorates the twenty-fifth anniversary of the discovery of the resolution principle, which took place during the summer of 1963. The CADE conferences are a forum for reporting on research on all aspects of automated deduction, including theorem proving, logic programming, unification, deductive databases, term rewriting, ATP for non-standard logics, and program verification. All papers submitted to the conference were refereed by at least two referees, and the program committee accepted the 52 that appear here. Also included in this volume are abstracts of 21 implementations of automated deduction systems.