The aim of the paper was to explore the reasons behind a perplexing observation that an intervention designed to alter professional behaviour in general practice consultations in South Wales was poorly sustained despite initial enthusiasm among the nurses. Nurses' baseline and continuing responses to the new approach with patients with non-insulin dependent diabetes are described, drawing on observations and interviews with the 18 practice nurses in the 15 experimental practices. The nurses fell into two groups: those showing greater understanding of the principles underlying the approach and a more reflective attitude to their work; and those who adapted the simple technology provided to their usual consultation style. This variation was related to their perception of their role and their attitudes to diabetic care, especially the challenge posed by the 'difficult patient'. They were noticeably less willing to allow the patient freedom to decide what to do once diabetic control was deteriorating according to biochemical measures. It is concluded that the failure of the nurses to sustain behaviour change over time stems from a basic dilemma, namely, what is the extent of my responsibility and how ought I to discharge it? There is scope for more research into professional perspectives on chronic care, the strategies they use to manage patients and to cope with their own feelings, and the implications of these strategies for patients.