Hutter, MarcusStephan, FrankVovk, VladimirZeugmann, Thomas2015-08-142015-08-140304-3975http://hdl.handle.net/1885/14723This special issue of Theoretical Computer Science is dedicated to the 21st International Conference on Algorithmic Learning Theory (ALT 2010) held in Canberra, Australia, October 6–8, 2010. It contains nine articles that were among the best in the conference. The authors of these papers have been invited by the Special Issue Editors to submit completed versions of their work for this special issue. Once received, these papers underwent the usual refereeing process of Theoretical Computer Science. In the following, we briefly introduce each of the papers.© 2012 Elsevier B.V.algorithmic learning theory2013-02-1810.1016/j.tcs.2012.10.007