This paper examines the potential for behaviour modification in the rehabilitation of chronic, long-stay psychiatric patients and the impact such procedures may have on the work role of ward-based nursing staff. Through the use of five case histories the effectiveness of behavioural analysis and modification in encouraging self-help skills and constructive activity is identified, In addition to a critical examination of the clinical and organizational factors involved in palienl improvement, it is argued that behaviour modification develops the therapeutic potential of nurses. The development of the patient-teaching dimension of the nursing role not only fosters greater clinical responsibility, but also promotes both professional independence and institutional power. This is not to imply that the use of behavioural methods cannot be combined with customary nursing practices, for in many ways they provide nurses with an appropriate technology to achieve established therapeutic goals. In conclusion, it is noted that clinical success is not sufficient to ensure the acceptance of ward-based behavioural programmes. The critical issues concern conventional hospital and staff practices and institutional rigidity, not the commitment of nursing staff or patient improvement.