There is a bidirectional involvement between the chronic kidney disease (CKD) and sleep apnea syndrome (OSAS). The declining of renal function, the fluid overloading and the disturbance of ventilation control could cause sleep apneas. On the other hand, the nocturnal hypoxia in patients with OSAS has been associated with changes in the renin-angiotensin system and sympathetic nervous system and production of reactive oxygen species. These findings are relationed with the deterioration of kidney function.