OBJECTIVES Our goals were to develop explanatory models to better understand how physicians diagnose and treat acute bronchitis; to describe patient expectations and needs when experiencing an episode of acute bronchitis; and to enhance communication between physician and patient. STUDY DESIGN We used qualitative, semi-structured, in-depth interviews to generate patient and physician explanatory models. POPULATION We had a purposely, homogeneous sample of 30 family physicians and 30 adult patients. OUTCOMES MEASURED Our multidisciplinary team of investigators used an editing style of analysis to develop patient and physician explanatory models based on the following topics: (1) what caused my illness/etiology, (2) what symptoms I had/onset of symptoms, (3) what my sickness did to me/pathophysiology, (4) how severe is my sickness/ course of illness, and (5) what kind of treatment should I receive/treatment. RESULTS We found that patient and physician models were congruous for symptoms of acute bronchitis and incongruous for etiology and course of illness. Models were congruous for treatment, although for different reasons. CONCLUSIONS Patients may have a very vague understanding of the process of infection and the difference between bacteria and viruses. Compounding this confusion is frequent miscommunication from physicians regarding the clinical course of untreated illness. These factors and non-communicated expectations from patients and fear of missing something on the part of physicians contribute to the decision to treat with antibiotics. [ABSTRACT FROM AUTHOR]