Context It is important to know how patients are affected by becoming opportunistically involved in medical student education. In previous studies, researchers rather than patients set the research agenda and expert patients or people well known to teachers were more often involved than ordinary people. Objectives This study aimed to explore how ordinary patients experience undergraduate medical teaching when they become involved in it opportunistically and to derive practical insights from the lived experiences of these patients. Methods The research was conducted in line with a conceptual orientation towards communities of practice theory and used phenomenology as a way of exploring patients' lived experiences in depth. Minimally structured interviews were carried out with 10 patients following ordinary out-patient or general practice appointments in which students were being taught. Template analysis was used to generate provisional themes and a process of phenomenological reduction was used to distil individual respondents' lived experiences to their essence. Results The presence of students in ambulatory consultations was normal. Nine respondents described transactional relationships in which they remained outside the community of practice of which the doctor and student were members. Only an intimate problem would engage them deeply enough for a student's presence to 'bother' them. One patient's personal and professional background led her to regard doctors' handling of consultation dynamics as factors contributing to whether teaching consultations were negative or positive experiences. When doctors' sensitive and inclusive behaviour drew her into a triadic relationship with the student and doctor, she experienced mutual benefits with students. When it did not, she felt objectified and alienated. Conclusions Provided they receive the clinical care for which they are attending a consultation and are treated respectfully, patients may sometimes willingly become 'objects' from which students learn. They may, however, become more deeply engaged in teaching consultations in which they participate actively in a triadic relationship of mutual benefit with a doctor and student. Teaching consultations call for doctors to be sensitive and adaptable.