The declaration of interest attached to Professor Mcdonald's letter is a clear answer to his question. It is almost impossible to exist as a medical practitioner without receiving support from one organisation or another at some point in your duties, but most of the time this is quite irrelevant to a piece of published information. The declaration of interest may need to be defined more specifically in our instructions but at present we are inclined towards the views of the BMJ in identifying those interests which are competing as those which should be declared. The BMJ defines a competing interest as one that ‘exists when professional judgment concerning a primary interest (such as patients’ welfare or the validity of research) may be influenced by a secondary interest (such as financial gain or personal rivalry)’ (http://www.bmj.com). This properly identifies the element that might, wittingly or unwittingly, create a bias in the written material that is submitted. In most instances the interest declared will be a financial one, but I would welcome more of the personal rivalry interests that are highly relevant in academic circles. Although not expecting ‘I am a visceral opponent of Dr X's work and cannot bear to be in the same room as him/her’, I think ‘I have a general bias against Dr X because I do not think he/she has the clinical experience to pronounce on these matters, whereas I have’, might not be out of place in an open and honest exchange of views.