The Community-Acquired Respiratory Distress Syndrome toxin (CARDS TX) is one of the most important toxins produced by the Mycoplasma pneumoniae. The synthesis, distribution and bioactivity of this toxin have been gradually studied. It has been shown that CARDS TX has impact on the inflammation induced by Mycoplasma pneumoniae infection, and poorly controlled asthma. With further study on the pathomechanism of the CARDS TX, it would become a new key in arriving early or confirmed diagnosis and treatment about Mycoplasmal pneumonia.