When confronted with patients who indulge in frequent self-induced vomiting one has to ask oneself the question ‘why do they do it?’ At the simplest level the answer to this question is that there are clear advantages to the patient from this behaviour. Patients can indulge their cravings for food to excess while at the same time avoiding the consequences in terms of weight gain. They can literally ‘have their cake and eat it’. The first therapeutic requirement is therefore to convince the patient that the disadvantages of self-induced vomiting, in terms of effects on physical health, far outweigh these benefits. Let us assume that we have been successful in this respect; the next step is to undertake a behavioural analysis.