This volume contains the proceedings of a summer school presented by the Centro Internazionale Matematico Estivo, held at Montecatini Terme, Italy, in July 1988. This summer programme was devoted to methods of global differential geometry and algebraic geometry in field theory, with the main emphasis on istantons, vortices and other similar structures in gauge theories; Riemann surfaces and conformal field theories; geometry of supermanifolds and applications to physics. The papers are mainly surveys and tutorials.