Mycoplasma pneumoniae is one of the common pathogens of the community-acquired pneumonia in adults and children. Macrolide antibiotics are considered to be the first-choice drug for M. pneumoniae infections. However, macrolide-resistant M. pneumoniae was first detected from Japanese pediatric patients in 2000,and it has been increasing over the past decade. On the other hand, the Immunocard Mycoplasma IgM test is widely used as a rapid and easy diagnostic method for M. pneumoniae pneumonia, but false-positive or false-negative cases have been reported in adults. Therefore new methods have been developed recently. Using the LAMP assay, the results are available rapidly and accurately. We report herein on two cases of M. pneumoniae bronchopneumonia in which the LAMP assay was useful in the diagnosis and treatment.