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 include: -Algorithms (sequential, parallel and geometric) -Automata theory -Functional programming -Learning -Logic of programs -Semantics -Structural complexity theory -Type theory.