OBJECTIVES: Mycoplasma pneumoniae is an atypical pathogen, which is one of the major causes of lower respiratory tract infections (LRTIs) worldwide. This study was performed to determine the role of M. pneumoniae in acute LRTIs in children, who were referred to main pediatric hospitals in Shiraz, Iran, with the diagnosis of LRTI. Polymerase chain reaction method on a throat-swab specimen was utilized to detect M. pneumoniae. RESULTS: One hundred patients with acute LRTIs were investigated in this study. There were 10 positive PCR for M. pneumoniae (10%), including 6 of 62 hospitalized patients and 4 of 38 outpatients. All patients with LRTIs due to M. pneumoniae had cough. Fever, flu like symptoms, dyspnea, pulmonary rales, wheezing, and conjunctivitis were other common signs and symptoms. CONCLUSIONS: The percentage of cases with M. pneumoniae infection in our population is similar to the reported in other parts of Asia. Precise and early detection of pathogen and appropriate antibiotic therapy are the key points in management of patients with LRTIs.