This book constitutes the refereed proceedings of the 16th International Conference on Principles of Distributed Systems, OPODIS 2012, held in Rome, Italy, in December 2012. The 24 papers presented were carefully reviewed and selected from 89 submissions. The conference is an international forum for the exchange of state-of-the-art knowledge on distributed computing and systems. Papers were sought soliciting original research contributions to the theory, specification, design and implementation of distributed systems.