Asthma is a disease in which airway hyperresponsiveness, increased airway contraction, and airway secretion occur as a result of allergic airway inflammation. Mycoplasma infections are well known to exacerbate asthma pathology as well as to cause the onset of asthma itself. Mechanisms of airway epithelial injury, activation of innate immunity, or increased Th2-dominant immune responses caused by community-acquired distress syndrome toxin (CARDSTx) or diacylated lipoprotein have been reported in exacerbations or the onset of asthma because of Mycoplasma infections. In addition, involvement of cysteinyl leukotriene and transforming growth factor beta has been reported in the increased airway hyperresponsiveness and exacerbation of airway remodeling by Mycoplasma. Recent evidence suggests that treatment with macrolides improves asthma control through an inhibitory action on airway inflammation as well as by eradicating Mycoplasma.