Many studies have reported that cancer patients who show difficulties maintaining perceptions of control report more psychological distress than patients who are hi.-her in control. Besides perceptions of control, feelings of illness uncertainty have also been regarded as a predictor of psychological distress. Given these strong relationships between perceptions of low control and high illness uncertainty and psychological distress, the present study examined whether an informational self-management intervention (booklet) could moderate this relationship. The booklet contained general and specific information about cancer and cancer treatment, information about possible coping strategies, and social comparison information. which consisted of short stories of other patients. Prior to radiotherapy, 209 patients with cancer completed baseline measures, including control and illness uncertainty. After completing radiotherapy, patients were randomly allocated to receive either a booklet (experimental group, N = 103) or no booklet (control groups N = 106). Three months after the intervention, aspects of psychological distress were assessed., including tension, anger. depression, fatigue and vigour. The results supported our hypotheses and suggested that a self-management intervention is relevant in reducing the relationship between control and illness uncertainty before radiotherapy and psychological distress after radiotherapy. This seems important, especially for high-risk patients who perceive little control and much illness uncertainty. Copyright (C) 2003 John Wiley Sons, Ltd.