The observational data presented by Macfarlaneet al on the aetiology of acute lower respiratory tract illness in the community1 confirm that the often stated assertion that these illnesses are usually caused by viral infection is incorrect. The high prevalence of bacteriological and atypical pathogens and, in particular, the high prevalence ofChlamydia pneumoniae in these patients is of interest and points to the need for further studies to clarify the clinical significance of these isolates. The lack of correlation between indirect evidence of infection (radiographic and CRP levels), GP assessment of the need for antibiotics, and pathogen isolation is also of great interest and …