Background: Sleep apnea-hypopnea syndrome (SAHS) is a cardiovascular risk factor. The aim of this study was to evaluate sleep disorders using polysomnography on a non-selected population of patients on maintenance hemodialysis. Methods: Overnight polysomnography was performed on 32 hemodialysis patients (24 men/8 women, 54 ± 16 years), and on 19 healthy subjects of similar age, sex and body mass index who were used as controls. Results: In hemodialysis patients, the most frequent sleep disorder was SAHS in 44% (14/32), followed by insomnia in 41% (13/32). Compared to healthy controls, patients on hemodialysis showed less slow-wave sleep and rapid eye movement sleep (23 vs. 36%, p = 0.001), less sleep efficiency (71 vs. 87%, p = 0.0079) and a higher periodic limb movement index (39.7 vs. 9.1; p = 0.003). An increase in apnea-hypopnea index (18.9 vs. 4.3; p = 0.007) and dips in the SaO<sub>2</sub> (≧4%) per hour of sleep (22.6 vs. 6.4; p = 0.021) were also significantly greater in hemodialysis patients than controls. 72% of the cases of SAHS were diagnosed solely by means of polysomnography. Conclusions: The patients on hemodialysis showed poor sleep quality with a significant increase in the apnea-hypopnea index and in the number of dips in SaO<sub>2</sub>. SAHS was underdiagnosed in a large percentage of the hemodialysis patients.