  This volume contains the proceedings of the Thirteenth Workshop on
Quantitative Aspects of Programming Languages and Systems (QAPL 2015), held in
London, UK, on 11 and 12 April, 2015. QAPL 2015 was a satellite event of the
European Joint Conferences on Theory and Practice of Software (ETAPS) focussing
on quantitative aspects of computation. The Program Committee of QAPL 2015
selected 8 regular papers and 2 presentation-only papers. The workshop
programme included two QAPL keynote presentations by Catuscia Palamidessi
(Inria/LIX, France) on "Quantitative Aspects of Privacy and Information Flow,"
and Holger Hermanns (Saarland University, Germany) on "Optimal Continuous Time
Markov Decisions."
