Mycotoxins are toxic secondary metabolites frequently produced by molds in waterdamaged indoor environments. The objectives of this work were to characterize the mycoflora (by microscopy and culture) and to study the prevalence of selected mycotoxins and levels of fungal biomass (by gas chromatography- and high pressure liquid chromatography tandem mass spectrometry) in samples collected by building inspectors from water-damaged indoor environments in Sweden during a one-year period. Sixty-six percent of the analyzed building materials (n=100), 11% of the settled dust samples (n=18), and 51% of the cultured dust samples (n=37) were positive for at least one of the studied mycotoxins. Except in the case of gliotoxin, mycotoxin-positive building material samples contained 2-6 times more ergosterol than mycotoxin-negative samples. The study result shows that the majority of molds contaminating indoor materials in Swedish water-damaged buildings produce mycotoxins, and that mycotoxin-containing particles settle on surfaces above floor level in these environments.