Background: The AIR II study is a prospective multicentre assessing management of lower respiratory tract infections (LRTIs) in adults by general practitioners (GPs). Epidemiological studies generally address the prescriptions of antibiotics. To our knowledge, little is known about the real impact of non-antibiotic therapeutic prescriptions (defined here as co-prescriptions) in LRTI. Therefore, the aim of the study was to evaluate non-antibiotic prescriptions in LRTIs. Methods: Two thousand general practitioners (GPs) were randomly selected and asked to participate in each of 30 predefined areas covering mainland France. The patient's sociomedical record was completed by the GP during the consultation and sent to the data processing centre at the same time as an anonymous copy of his prescription. The GP also had to report the inclusion by telephone and agree to a telephone appointment with an interviewer. Results: GPs (n=3144) reported 5469 evaluable cases. Pneumonia accounted for 9.6% of diagnoses, acute exacerbations of chronic bronchitis 14.9% and acute bronchitis 72.5%. Antibiotics were prescribed to 96.5% of patients. In addition to the 5270 prescriptions of antibiotics, co-prescriptions proved to be twice as numerous as prescriptions of antibiotics (10,027 prescriptions for 5115 patients). Mucomodifiers, steroidal anti-inflammatory drugs and bronchodilators were significantly more prescribed in AECB than others. Non-steroidal anti-inflammatory drugs and antitussives were significantly more prescribed in acute bronchitis than AECB or CAP. Conclusions: Our results suggest that recommendations of management in LRTIs need to take into account co-prescriptions.