While the importance of patient autonomy is widely acknowledged and discussed in the bioethics literature, clinicians' autonomy, their ability to make the best choices about patients' care free from outside interference, is far less debated. This paper takes one form of external influence over clinical decisions - the cost of drugs - and applies it to a specific case, that of HER2 positive breast cancer and the use of the drug Herceptin in the UK. Drawing on interviews with clinicians, researchers and policymakers, I explore the way financial decisions about Herceptin shape clinicians' autonomy, and how clinicians as individuals and as professional groups respond to these limits and seek to provide treatment to the highest number of the most deserving patients they can. The point of this paper is not to castigate bioethicists for misguidedly focusing on patient autonomy but point out that clinicians' autonomy may be so circumscribed by external factors that it may make no sense to speak of their actions as stemming from ethical decisions. At the same time, I suggest that financial constraints create areas at the margin of clinical practice which are deserving of bioethical consideration.