This volume contains papers presented at the 17th Annual Conference on Le- ning Theory (previously known as the Conference on Computational Learning Theory) held in Ban?, Canada from July 1 to 4, 2004. The technical program contained 43 papers selected from 107 submissions, 3 open problems selected from among 6 contributed, and 3 invited lectures. The invited lectures were given by Michael Kearns on Game Theory, Automated Trading and Social Networks, Moses Charikar on Algorithmic Aspects of - nite Metric Spaces, and Stephen Boyd on Convex Optimization, Semide?nite Programming, and Recent...