In recent years, in the field of conservation and protection of excavation areas, there has been a growing conviction that preventive conservation – especially maintenance – is one of the most suitable tools for effective and extensive conservation, as it is the most practicable in cost-benefit terms. This discipline, which has only recently appeared on the conservation horizon, has its origins in antiquity. It offers a valid reply to the disproportion between the exigencies of conserving an ever-increasing amount of heritage and the growing demand for access by new generations of visitors. In this article, techniques for the conservation and maintenance of mosaics in situ in archaeological areas will be discussed. This will be done by revisiting the sources and describing the modern techniques, proposing a methodological approach and supplying evaluations of the techniques, costs and results obtained. Archaeological mosaics displayed in museums, albeit numerous and not without maintenance problems themselves, will not be discussed, as they call for different conservation considerations and treatment techniques.