This volume contains the proceedings of the SeventhInternational Conferenceon the Mathematical Foundations ofProgramming Semantics, held at Carnegie Mellon University,March 1991.The conference continued a series of annual meetings,alternating between workshop and conference formats,intended to bring together computer scientists andmathematicians for discussion of research problems, resultsand directions in programming language semantics and relatedareas. A major goalof the series is to improvecommunication and interaction between researchers in theseareas and to establish ties between related areas ofresearch.The volume contains revised and refereed versions of each ofthe contributed papers and refereed papers by three invitedspeakers:Jon Barwise, John Reynolds, and Mitchell Wand.