Mold can cause sensitization and clinical disease. Skin prick and in vitro tests can effectively identify patients who are sensitized to molds, although this does not always translate to clinical disease. Results of these tests must be interpreted in the context of the patient’s clinical presentation. Exposure to dampness and mold can increase the risk of developing asthma in children regardless of their atopic status and increased symptoms of asthma and rhinitis in individuals who already have these conditions. Interventional studies have found that a multifaceted series of interventions aimed at reducing indoor moisture, removing contaminated building materials, and reducing reservoirs (including carpeting and dust) can reduce exposure sufficiently to reduce symptoms in affected individuals. This implies a causal relationship between exposure to fungi and morbidity and provides a rationale for environmental interventions to reduce it.