DCFS 2012, Descriptional Complexity of Formal Systems, will be held in Braga, Portugal on July 23-25, 2012 and will be jointly organized by University of Porto and University of Minho with the support of University of Beira Interior. Descriptional complexity is a multidisciplinary area of study that includes descriptional randomness on computational complexity, cryptography and information theory; resource-bounded or structure-bounded complexity; frontiers between decidability and undecidability; and universality and reversibility.