OBJECTIVES: To study and report the attitudes of patients and general practitioners (GPs) concerning the obligation of doctors to act for the good of their patients, and to provide a practical account of beneficence in general practice. DESIGN: Semi-structured interviews administered to GPs and patients. SETTING AND SAMPLE: Participants randomly recruited from an age and gender stratified list of GPs in a geographically defined region of South Australia. The sample comprised twenty-one general practitioners and seventeen patients recruited by participating GPs. RESULTS: In practice, acting for the good of the patient not only accommodates the views of patients and GPs on expertise and knowing best, but also responds to the particular details of the clinical situation. Patients had a complex understanding of the expertise necessary for medical practice, describing a contextual domain in which they were expert, and which complemented the scientific expertise of their GPs. General practitioners identified multiple sources for their expertise, of which experience was the most significant. The role of the GP included responding to individual patients and particular clinical problems and ranged from the assumption of responsibility through to the proffering of medical advice. CONCLUSION: This study found that GPs acting for the good of their patients covered a variety of GP actions and patient preferences. Beneficence was not justified by presumed patient vulnerability or the inability of patients to understand medical problems, but furthered through a recognition of the different areas of expertise contributed by both parties to the consultation.