This volume contains all the papers that were presented at the Fourth Workshop on Algorithmic Learning Theory (ALT '93), which was held at University of Electro-Communications in Tokyo from November 8th to 10th, 1993. In addition to 3 invited papers, 29 papers were selected from among 47 submitted extended abstracts, which represent the highest number of papers submitted to an ALT workshop, exceeding 46 which were recorded in 1990.