Little attention has been paid to sleep disturbance experienced by advanced cancer patients. The purpose of the present study was to investigate longitudinal change in sleep disturbance and to identify factors that associated with and predicted sleep disturbance among 209 consecutive terminally ill cancer patients. Patients were assessed twice for sleep disturbance by one item of the structured clinical interview for assessing depression, once at the time of their registration with a palliative care unit (PCU) (baseline) and again at the time of their PCU admission (follow-up), and possible associated medical and psychosocial factors were evaluated. The proportions of patients with obvious sleep disturbance at baseline and follow-up were 15.3 and 25.9%, respectively. Sixty-seven percent of the subjects showed some sleep status changes, including both aggravation and improvement, between baseline and follow-up. Being younger, having diarrhea and living alone were significantly associated with sleep disturbance at baseline, and the increase of psychological distress was the only significant predictive factor for sleep disturbance at follow-up. These findings suggest that psychological distress is a possible key cause of sleep disturbance and management of psychological distress may be one promising strategy for prevention of sleep disturbance among advanced cancer patients. Copyright (C) 2006 John Wiley & Sons, Ltd.