This book constitutes the refereed proceedings of the 9th International Conference on Algebraic Methodology and Software Technology, AMAST 2002, held in Saint-Gilles-les-Bains, Reunion Island, France in September 2002. The 26 revised full papers presented together with 6 invited papers and 2 system descriptions were carefully reviewed and selected from 59 submissions. Among the topics covered are all current issues in formal methods related to algebraic approaches including abstract data types, process algebras, algebraic specification, semantic specification, model checking, mu-calculus, Petri box algebras, unification, verification of Java for smart cards, security, JML specification, and formal software development.