Among 199 cases of bronchopulmonary infection in children observed over a 2-year period, 22 cases (11%) were due to Mycoplasma pneumoniae. The diagnosis was based upon the complement fixation test on whole serum in half of the children and the research of specific IgM by complement fixation test on fractioned serum and/or indirect immunofluorescence on the others. The mean age of children with Mycoplasma pneumoniae was 6 years. The clinical and radiographic appearance of the affection was non specific, often similar to pneumococcal pneumonia.