22 papers focusing on the problems of preserving sites and artifacts left in situ were presented at an international conference organized by the Instituto Nacional de Antropologia e Historia (INAH) and the Getty Conservation Institute (GCI) in Mexico City in April 1986. The first part deals with how best to preserve sites endangered either by their remoteness from urban areas or the encroachments of urbanization. The second part deals with materials found in excavations that cannot be left in situ. A third section presents case studies in Mexico. The participants came from or wrote about their work in Algeria, England, Canada, the Arctic zone, Peru, Turkey, Sweden, and in largest numbers, Mexico. Throughout these papers, the need for cooperation among interdisciplinary teams is stressed. The aim of the conference was to provide a survey of archaeological field techniques, to report on the current state of knowledge of the methods used to preserve excavated material, and to discuss the sites themselves. The foreword was contributed by Brian V. Arthur. -- AATA