Occurence and hygienic/allergological relevance of mould from point of view of the environmental medicine Allergic skin and respiratory diseases range among the most frequent afflictions in industrialized countries. Due to this fact the importance of indoor mould pollution based on dampness is discussed. In a sentinel health study of the State Health Agency (LGA) children attending Class 4 of a primary school were tested by an in-vitro allergy screening (UniCap 100/Phadia) for the mould allergens mx 1 (Penicillium chrysogenum ml, Cladosporium herbarum m2, Aspergillus fumigatus m3 und Alternaria altemata m6). Primarily about 5% of the children were sensitized against mould which are associated with the ambient air. The investigations showed that most of the children were sensitized against Alternaria altemata and concerning the IgE-concentration (kW) Alternaria alternata had the highest concentration among the tested allergens. Commonly children with sensitization against mould were polysensitized. It is unclear if the allergy screening against mould mx 1 includes mould with indication for indoor mould pollution such as Acremonium spp., Aspergillus penicillioides, Aspergillus restrictus, Aspergillus versicolor, Chaetomium spp., Phialophora spp., Stachybotrys chartarum, Tritirachium (Engyodontium) album und Trichoderma spp. by means of crossreaction. Therefore such investigations do not admit any conclusion about health problems as a result of indoor mould pollution. At the present state of knowledge the exposure measurements of indoor mould pollutions are not possible, at most a semi-quantitative assessment. Although it is generally accepted that dwellings with moisture and mould represent a health risk, knowledge about indoor mould pollution and the related health problems is lacking.