The knowledge on the role of M. pneumoniae in human respiratory tract infections especially in infants and children has advanced in the past two decades. The understanding of its incidence, clinical presentations, pathology & pathogenesis, laboratory diagnosis, complications and late sequelae, treatment, prevention and epidemiological aspects place it as an important aetiological agent in the pediatric patients. It should be considered in the differential diagnosis of all pneumonias. Further studies are needed to solve many observations on the role of mycoplasma in diseases of man.