PURPOSE: To analyze the HRCT findings of adult mycoplasma pneumonia and correlate these with clinical information. MATERIALS AND METHODS: HRCT was performed in 17 cases of 15 adult patients (M:F=5:10) in whom mycoplasma pneumonia had been serologically confirmed. The pattern, extent and distribution of abnormalities were reviewed retrospectively and a changing pattern of abnormalities during the course of the disease was correlated with clinical symptoms. RESULTS: Unilateral(n=11) and lower lobe(n=12) involvement and multiplicity in involved lobes(n=10) were the most common abnormalities. Abnormalities on HRCT were as follows : nodules(n=15), areas of consolidation(n=14), nodules and areas of consolidation(n=13). Most abnormalities(n=11) were segmental or subsegmental in distribution. The most common nodular pattern was centrilobular micronodules(<5mm) or branching linear structures(n=15). An air-bronchogram in areas of consolidation was noted in 13 of 14 cases(92.9%). Areas of ground-glass attenuation, bronchial wall thickening and dilatation were observed in 11 cases as part of a mixed pattern. Additional findings were interlobular septal thickening(n=9), air-trapping(n=1), pleural effusion(n=2),and mediastinal lymphadenopathy(n=1). The relationship between the pattern of abnormalities and duration of the disease(from the onset of symptoms to the time of HRCT scan) was as follows. Group 1 (similar area ratio of consolidation and nodules) was predominant at 1 week, Group 2 (prominent areas of consolidation(>2/3)) at 2 weeks,and Group 3 (prominent areas of nodules(>2/3)) over 3 weeks. CONCLUSION: The main findings of adult mycoplasma pneumonia were nodules or areas of consolidation with segmental or subsegmental distribution. The early stage of the disease may show a pattern of a similar propartion of areas of consolidation and of nodules, followed by an increase in the propertion of areas of consolidation(>2/3) as the disease progresses. At the resolvtion stage, the extent of lesions will decrease and nodules will be the main finding.