The International Conference on Quantitative Evaluation of SysTems (QEST) is the leading forum on evaluation and verification of computer systems and networks, through stochastic models and measurements. Performance metrics of interest include response time, reliability, availability, safety, security, survivability, correctness, timeliness, and efficiency. Areas of interest include modelling formalisms and methodologies, measurements, analytical and numerical evaluation, simulation and verification, and theory of probabilistic, concurrent and non-deterministic behaviour. Also of interest are case studies showing the role of quantitative evaluation in the design of systems including computer architectures, distributed and fault tolerant systems, communication systems, embedded systems, web-based systems, and safety-critical systems. Moreover, tools for supporting the practical application of research results in all the above areas are of special interest for QEST and therefore tool papers are sought. In short, QEST aims to create a sound methodological basis for assessing and designing trustworthy computing systems and networks.