We studied 143 cases of serologically proven(cold agglutinin or 1HA test) M. Pneumonia in children below 15 year of age who admitted to Wallace Memorrial Baptist Hospital between March 1986 and August 1988. The following results were noted : 1. Radiologic findings The patterns of lung infiltration were bronchopneumonic in 52.6%, interstitial in 24.5%, lobar in 3.5%, mixed in 1.3%, and normal or slightly increased bronchovascular markings in 18.1%. The degree of pulmonary involvement were minimal in 49.2%, moderate in 24.5% and extensive in 8.3%. The distribution of infiltration in the minimal and moderate pulmonary involvement were upper lobe in 28.6%, middle lobe in 17.2% and lower lobe in 54.3%. Other findings were bilateral involvement in 31.5%, pleural involvement in 15.8%, new area of consolidation in 53.5% and hilar lymph node involvement in 34.2%. 2. The most common duration of the period between the onset of symptom and confirmation of the diagnosis was 7-14 days. 3. T e sex distribution was 1.3 : 1 in male to female ratio. 4. The most peak age incidence was seen in 10-13, and the second one in 4-7 year. 5. As for the concomittant illness and complication, asthmatic bronchitis was most common(23 cases, 16.1%) followed by pharyngitis, sinusitis, skin rash and gastroentritis, etc.