This book is an expanded version of the notes from a seminar on
intersection cohomology theory, which met at the University of Bern,
Switzerland, in the spring of 1983. This volume supplies an introduction
to the piecewise linear and sheaf-theoretic versions of that theory as
developed by M. Goresky and R. MacPherson in Topology 19 (1980), and
in Inventiones Mathematicae 72 (1983). While some familiarity with
algebraic topology and sheaf theory is assumed, the notes include a
self-contained account of further material on constructibility, derived
categories, Verdier duality, biduality, and on stratified spaces, which
is used in the second paper but not found in standard texts.