This volume contains the 31 papers presented at the first international workshop on Algorithmic Learning Theory (ALT '90) which was held in Tokyo, 8-10 October 1990. This workshop was the first meeting on this subject sponsored by the Japanese Society for Artificial Intelligence, and it is expected that future ALT workshops will be held every two years. Recent research on AI systems has indicated that 'learning ability' is fundamental to the development of intelligent computer software and of information systems in areas such as natural language understanding, pattern recognition, and robotics. The main aim of this workshop was to provide an open forum for intensive discussions and the exchange of academic information among researchers in the area of algorithmic learning theory. From the 46 extended abstracts submitted, 28 papers were selected for inclusion in this volume, with authors from the USA, the UK, Japan, the USSR, India, and continental Europe. Besides the 28 selected papers, the program committee invited 3 lectures by distinguished researchers: "Mathematical Theory of Neural Learning" (by S. Amari, University of Tokyo), "Decision Theoretic Generalizations of the PAC Learning Model" (by D. Haussler, University of California), and "Inductive Logic Programming" (by S. Muggleton, The Turing Institute, Glasgow).