Until very recently it has been customary, at least in this country, to present the homoeopathic approach to chronic disease largely in terms of ‘constitution’. Newcomers to the subject often find the idea of constitution hard to grasp, but this has not usually deterred its advocates from insisting on its fundamental importance.The generally accepted version of the constitutional idea appears to be something as follows. In selecting a remedy to treat a case of chronic disease, the prescriber should endeavour to identify certain physical and dispositional characteristics of the patient and should then match these with a “drug pictureâ€? (usually a polychrest). This is the patient’s “constitutional remedyâ€?, which is given in high potency as a single (or “split singleâ€?) dose.In recent years there has been a good deal of discussion about the notion of constitution-whether it can be verified objectively, whether different prescribers will see the same constitutional picture in a given individual, and so forth. Some homoeopaths have suggested that research into these questions should be carried out by means of questionnaires to measure personality profiles and the like. It seems to me, however, that before embarking on elaborate research projects of this kind we ought first to ask ourselves some much simpler and more fundamental questions, such as: 1. How did the constitution idea get into homoeopathy in the first place? 2. Is it really as central to homoeopathy as seems to be believed by many modern homoeopaths? 3. Is the idea a coherent one anyway?In this paper I propose to try and answer these questions. I must emphasize at the outset that what I shall be talking about is the concept of constitution in homoeopathy. The constitution idea has of course a very long history outside homoeopathy; it goes back at least as far as Aristotle and in more recent times there have been various typological schemes such as those of Sheldon and of Jung. To discuss these would take far too long and would not shed much light on the peculiar nature of the problem in homoeopathy.