Optimistic concurrency has long been accepted as a convenient method for programming systems where there is contention for resources. Traditionally in database systems and more recently in software transactional memory systems, optimistic concurrency is realized in the form of transactions, which the programmer can assume run isolated from their environment, thereby alleviating the need for explicit programming of locking schemes. Recent research on concurrent programming models have lead to the realization in both academia and industry that optimistic concurrency can also be advantageous in programming systems where concurrent processes need to cooperate to perform a desired task. In such systems transactional isolation needs to be abandoned. This brings forward numerous challenges in 1) the design and implementation of such systems, 2) the invention of appropriate programming language support for optimistic process cooperation, 3) the semantics, theory and verification of these systems. This workshop aims to bring together researchers and practitioners from academia and industry who work on aspects of optimistic process cooperation. It also aims to connect the different research communities pertinent to this field. These include the programming language community, the systems community and the concurrent calculi community. Vasileios Koutavas (Trinity College Dublin, Ireland) Matthew Hennessy (Trinity College Dublin, Ireland) Nick Benton (Microsoft Research, Cambridge, UK) Jens Palsberg (UCLA, USA) Matthew Fluet (Rochester Institute of Technology, USA) Abstract submission: 14 December 2012 Paper submission: 21 December 2012 Notification: 25 January 2013 Camera ready of preliminary proceedings: 22 February 2013 Dates: Saturday March 16th, 2013