This book constitutes the refereed proceedings of the First International Joint Conference on Automated Reasoning, IJCAR 2001, held in Siena, Italy, in June 2001. The 37 research papers and 19 system descriptions presented together with three invited contributions were carefully reviewed and selected from a total of 112 submissions. The book offers topical sections on description, modal, and temporal logics; saturation based theorem proving, applications, and data structures; logic programming and nonmonotonic reasoning; propositional satisfiability and quantified Boolean logic; logical frameworks, higher-order logic, and interactive theorem proving; equational theorem proving and term rewriting; tableau, sequent, and natural deduction calculi and proof theory; automata, specification, verification, and logics of programs; and nonclassical logics.