Preventive conservation, in contrast to conservation and restoration treatment of objects, is preservation of the objects against decay, and prevention of damage. Actual treatment of objects involves the risk of failures, also due to possible incompatibility of materials, and should be carried out by well-trained and experienced restorers. In daily housekeeping we prevent the decay and damage (mainly) of objects, even of those we do not wish to keep after they have been worn and torn. The great difference between museum objects and private property is that we must preserve the former. The latter we may use and keep or throw away as we please. Decaying museum objects gradually lose their content of historic information and their aesthetic and financial value. Preventive conservation makes sense because it serves a whole collection, economizes because investments have long lasting returns and is realistic because without it the safe-keeping of cultural property is an illusion. Six conditions are involved in conservation: the good will and determination to safeguard and keep the collection, a proper registration of the collection, the right choice of the environment for the objects, good storage facilities, well-trained and responsible employees and, for thoroughness, a disaster control plan. The Dutch Government's Delta Plan aims at providing financial support for the fulfilment of these conditions. A bibliography of 25 titles is included in the paper.