Different methods were evaluated for their potential to show unusual microbial conditions in a building. The buildings studied were schools and offices. The buildings were inspected for visible signs of moisture by a civil engineer. Samples were taken from the air, surfaces and structures. Indoor air concentrations of viable microbes were higher in moldy than reference buildings. This difference could not be seen in the total counts of biological particles. In most cases, the concentrations of microbes on the surfaces were low. In some cases microbial concentrations were high in material samples although no contamination could be seen in surface swab samples from the same damage area. With one sample or one method alone, the conclusion of the mold problem in the building could not necessarily be drawn.