Mycoplasma pneumonia is a cause of primary atypical pneumonia, but it is asymtomatic mostly or may cause of only mild symptoms. School-aged children experienced high attack rateand mainfestations of "unusual pneuonia" are noted. So authors reviewed clinical and radiological features of 110 case of serologically proven Mycoplasma pneumonia in hositalized children between November 1984 and January 1987 retrospectively. RESULT : 1. The sex distribution was 57:53 in male to female ratio and 47% of them were 5 through 8 years old of age with peak incidence between 5 and 6 years old of age. 2. The symptoms were cough, fever, and sore throatin decending order of frequency and mean symptom duration before admission was 8.1 day. The prevalent season was earlier winter. 3 The radiologic findings were air-space consolidation with lobar, segmental distribution in 68%, interstitial infiltration in 12%, bronchopneumonia in 12%, chronic bronchitis pattern in 3.6%, normal in 4.5%, hilar LN en argement in 37%, pleural effusion in 12%. 4. Radiologic resolution period was usually 10 days around and after complete recovery, scarrig change or calcification was not seen. 5. Extrapulmionary manifestations were uncommon but hepatitis, hematuria, skin rash, gastroenteritis, myocarditis, otitis media occurred. 6. With administration of tetracyclin and erythromycin, clinical and radiologic responses were promptly seen.ptly seen.