This volume is based on a meeting on Quantum Mechanics of Fundamental Systems, held December 17-20 of 1987, at the Centro de Estudios Cientificos de Santiago (CECS). The meeting was intended to review new developments in the field defined by its purposely vague title. We were especially interested in communicating important advances in a broad perspective and in a self-contained manner to a wide colleague­ ship, and in particular to Latin American physicists. Whatever success we may have achieved in that direction would cer­ tainly not have been possible without the help and generosity of many people. For their kind support we thank the Tinker Foundation, the Inter­ national Centre for Theoretical Physics, the Ministere des Affaires Etrangeres et Service Culturel et de Cooperation Scientifique et Technique de France and the Centro Latinoamericano de Fisica. We are especially grateful to the Santiago College and to its principal, Rebeca Donoso, for allowing us to hold the meeting at that school when, at the last moment, we were deprived of the previously arranged meeting site. Last but not least we thank the participants for an extraordinary week and the CECS staff for performing, as usual, beyond any reasonable expectation.