This volume contains the proceedings of the Eleventh Conference on Foundations of Software Technology and Theoretical Computer Science held in New Dehli, India December 17-19, 1991. Three invited papers and 25 contributed papers selected from 78 submissions by authors from many different countries reflect the current research concerns of the theoreticalcomputer science community. The topics covered -Algorithms (sequential, parallel and geometric) -Automata theory -Functional programming -Learning -Logic of programs -Semantics -Structural complexity theory -Type theory.