Daily observations of patients with end-stage renal disease have shown us that a significant number of them take a ''nap'' during the hemodialysis treatment. Our major concern was to investigate whether this behavior was compensation for a modified sleep profile at home, or simply a way to cope with the 4-hour treatment sessions. The purpose of this study was to evaluate the sleep disturbances associated with regular hemodialysis treatment, especially in relation to treatment schedule and the duration of hemodialysis therapy One hundred thirty-five patients (mean age, 59.0 +/- 13.2 years) were studied using a modified post-sleep inventory (PSI). Patients were assigned to three groups according to their treatment schedule, i.e., morning, afternoon, or late evening. One-way ANOVA and contingency analysis were used. The majority of the patients (53.3%) reported that they sleep well. Regular dialysis treatment, in and of itself, did not seem to be negatively correlated with sleep quality; however, the schedule of the hemodialysis treatment did appear to influence sleep quality: Patients who were dialyzed in the morning reported less nocturnal sleeping hours and less hours of lying in bed, and showed a tendency to have higher PSI scores. A prolonged number of years on hemodialysis therapy also seemed to contribute to an increase in sleep disturbances. In conclusion, patients who have been on hemodialysis therapy for many years, as well as those with sleeping problems in general should be allowed to choose the afternoon or late-evening shift.