In conjunction with PODC 2012, the TransForm project (Marie Curie Initial Training Network) and EuroTM (COST Action IC1001) supported the 4th edition of the Workshop on the Theory of Transactional Memory (WTTM 2012). The objective of WTTM was to discuss new theoretical challenges and recent achievements in the area of transactional computing. The workshop took place on July 19, 2012, in Madeira, Portugal. This year's WTTM was a milestone event for two reasons. First, because the same year, the two seminal articles on hardware and software transactional memories [15, 21] were recognized as outstanding papers on principles of distributed computing, whose significance and impact on the theory and practice of distributed computing have been evident for at least a decade. Second, the winners of this prestigious ACM/EATCS Edsger W. Dijkstra Prize, Maurice Herlihy, Eliot Moss, Nir Shavit and Dan Touitou, were present at the workshop and three of them discussed their current progress with other outstanding researchers from the field. This report is intended to give highlights of the problems discussed during the workshop.