Control of biological growth is one of the operations carried out on cultural heritage during restoration. Chemical substances, biocides, are usually used for this purpose; they are applied before and/or after restoration and conservation treatments. Generally, biocides are used to eliminate the macro- or microflora responsible for biodeterioration, although more recently some products have been developed to prevent new microbial colonization of restored surfaces and consequently should be applied at the end of the conservation treatment (Malagodi et al., 2000; Urzi et al, 2000). For the conservation of stone materials, many studies have been carried out on commercial biocides to test their effectiveness, toxicity level, chemical stability, and harmlessness for treated surface, in order to identify the most suitable products (Koestler and Salvadori, 1996; Tiano, 1998; Warscheid and Braams, 2000). Unfortunately, the results of laboratory and in-situ tests often provide information on a single case or on a specific problem without taking into account the overall conservation project for the monument in question. The control of biological growth requires further in-depth analysis, which should fulfill the following aims: Evaluate the efficacy of chemical products against macro- and microorganisms deteriorating stone (target biodeteriogens); Assess the substrate-biocide interaction; Define methods for testing and evaluating biocides; Define the best method for applying biocide on stone; Evaluate long-term effects of biocide applications and interactions with other products used during restoration; and Single out new and alternative methods to disinfect and de-infest.