The following agents of stone deterioration are reviewed: air pollution, freezing, rain and soluble salts. Examples of monuments in Greece which are suffering from these various forms of deterioration are given. Problems which consolidants have presented over time help us to determine which rules to follow today in the conservation treatment of stone: 1) do not obstruct the movement of soluble salts in the object but protect the object from sources of soluble salt contamination, 2) maintain as steady a relative humidity and temperature as possible, avoid exposure to wetting/drying cycles, 3) do not treat the objects with surface coatings in order to protect them from deterioration by air pollutants but instead protect them from polluted air. The various protection materials which in the past were considered efficient have today been proved largely unsuccessful since they can create more problems than they solve. Today we experience a strong tendency towards more traditional stabilization materials, we search for new protective materials, and attempt to treat the cause of the deterioration rather than the products of deterioration. Included is a bibliography dealing with the deterioration of stone and methods for its protection. -- AATA