This paper conceptualizes a type of physician communication, termed 'online commentary'. Online commentary is talk that describes what the physician is seeing, feeling or hearing during physical examination of the patient. Some dimensions of online commentary are described, and its functions in routine and acute medical consultations are distinguished. Using a case study method, the paper focuses on the role of online commentary in pre-empting patient resistance to upcoming 'no problem' diagnostic evaluations which could delegitimize patients' decisions to seek medical assistance, or deprive them of anticipated medical benefits. It is hypothesized that this role for online commentary may be associated with successful physician resistance to implicit or explicit patient demands for inappropriate antibiotic medication.