This book constitutes the refereed proceedings of the 12th International Conference on Algorithmic Learning Theory, ALT 2001, held in Washington, DC, USA in November 2001. The 21 revised full papers presented together with two invited papers and an introduction by the volume editors were carefully reviewed and selected from 42 submissions. The papers are organized in topical sections on complexity of learning, support vector machines, new learning models, online learning, inductive inference, refutable inductive inference, learning structures and languages.