Sick house syndrome is caused by not only chemicals but also dampness and biological factors. Many European and North American studies have shown that dampness associated with condensation, visible mold, moldy odor, and water-induced damage among others affects residents’ health. Recent Japanese studies have also shown a similar significant relationship. Mold can cause infection and allergy, and can produce chemicals such as microbial volatile organic compounds (MVOCs) and (1→3)-β-D-glucan. Mold exposure can be analyzed using culture-based (colony forming unit count) enumeration techniques. More recently, other nonculture-based methods of measuring mold concentrations in indoor environments have been described, which may provide more valid measures of exposure. These are based on measurement of specific mold markers in dust or air, such as ergosterol, genus-specific extracellular polysaccharides or (1→3)-β-D-glucan. Mites are major indoor allergens. The gold standard for measuring exposure to mite allergens is enzyme-linked immunosorbent assay (ELISA), but it is relatively expensive and requires specialized techniques. Several simple semiquantitative dust mites allergen test have b available in Japan.