Specific laboratory tests of biodeterioration were investigated by many laboratories. The selection of the most suitable method was dependent on the type and the stage of organisms which were deteriorating buildings. Sometimes a good effect was obtained by the combination of many methods which were successfully applied on architectonic monuments. Before any cyanobacteria or algae removal methods are used on stone, their reaction on the substrate and effectiviness as algal inhibitors or eradicators must be assessed for each specific site. The environmental control of stone-monument sites should be looked at as a logical method of algal control such as the reduction of humidity, protective coating, drainage, impregnation, etc. Perhaps these natural methods of control are the answer. In this study I have focused on subaerial microalgae inhabiting deteriorated monuments. I investigated taxa of these groups in the urban habitats. The aims of this study were specified thereinafter: 1. floristic screening of microalgae causing the biological attack on building stone; 2. Which factor of urban environment (substrata, pollution, humidity, etc.) have an influence on the composition of the subaerial taxa; 3. To set a growth inhibition test on subaerial microalgae; 4. To test a microalgae causing actively biodeterioration which potentially damage the building stone. Acknowledgement: Financial support for this study was provided by the Funding of Ministry of Education of Czech Republic; project No. MSM0021622416.