BACKGROUND AND RESEARCH QUESTION: Physicians' decisions regarding the indication of medical treatment are central to the application or limitation of medical measures in advanced cancer. This qualitative study explores criteria and procedural aspects of treatment decisions with patients with cancer near the end of life from the perspective of oncologists. RESEARCH PARTICIPANTS AND METHODS: In this qualitative interview study physicians working in the field of oncology were asked about their decisional criteria and procedural aspects of treatment decision making in cases of patients with advanced cancer. All interviews were audiotaped and transcribed. Qualitative data analysis was conducted in accordance with principles of "Grounded Theory". RESULTS: 17 research interviews had been analysed. Next to medical criteria the life-circumstances of the patients with respect to age and social situation as well as the perceived quality of the physician-patient-relationship were named as foundation for decisions about the application or limitation of medical treatment at the end of life. In addition situational factors such as time pressure or the available technical equipment were cited as relevant factors for the decisions. "Silent acquiescence" as the predominant decision making model which has been reconstructed on the basis of the narratives means that decisions about the limitation of medical treatment are not communicated explicitly within the physician-patient-relationship. This approach was justified by the interviewees in light of the long standing relationship between physicians and patients. CONCLUSIONS: The decisional criteria and procedural aspects of decision making in patients with advanced cancer which have been elicited in this qualitative study inform the current scientific and societal debate on ethically relevant aspects of end-of-life decision making in medicine.