This volume contains all the papers that were presented atthe Fourth Workshop on Algorithmic Learning Theory, held inTokyo in November 1993. In addition to 3 invited papers, 29papers were selected from 47 submitted extended abstracts.The workshop was the fourth in a series of ALT workshops,whose focus is on theories of machine learning and theapplication of such theories to real-world learningproblems. The ALT workshops have been held annually since1990, sponsored by the Japanese Society for ArtificialIntelligence. The volume is organized into parts oninductive logic and inference, inductive inference,approximate learning, query learning, explanation-basedlearning, and new learning paradigms.