Dear Colleagues, This is the first Call for Participation at MFPS XXVII, the Twenty-seventh Conference on the Mathematical Foundations of Programming Semantics, which will take place on the campus of the Carnegie Mellon University, Pittsburgh, PA, USA, from May 25 to May 28, 2011. The meeting will include plenary lectures by Steve Brookes (CMU), Jérôme Feret (INRIA), John Reynolds (CMU), Alex Simpson (Edinburgh), Stephanie Weirich (Penn) and Steve Zdancewic (Penn). The program also includes a special session honoring John Reynolds on his 75th birthday, a session on systems biology, and a session on security, as well as tutorial lectures on "Programs from Proofs", and fourteen contributed talks selected by the PC for presentation at the meeting. Complete details about the program can be found at the web site http://www.math.tulane.edu/~mfps/MFPS27 Registration is now open, and registration information for the meeting also is available on the web site. Any questions can be directed to mfps@math.tulane.edu Best regards, Mike Mislove Joel Ouaknine, Chair, Program Committee [For admin and other information see: http://www.mta.ca/~cat-dist/ ]