Background and design. - We have evaluated the features of 20 atypical pneumonia cases caused by Mycoplasma pneumoniae in 1994. The diagnosis of MP was made by high titers of MP IgM. The patients were treated with claritromycin for 14 days and 95 % of the cases were cured. One patient died because of bronchiolitis obliterans. Radiological investigation revealed bilateral (45 %) involvement of the lower lobes (80 %), and pleural fluid (20 %).