Obstructive sleep apnea (OSA) during rapid eye movement (REM) sleep is defined as OSA occurring mainly in the REM sleep. Evidence shows that REM sleep is associated with abnormal higher sympathetic activity, so OSA in this period leads to even higher sympathetic activity, and thus cardiovascular instability. Recent studies have indicated that REM-OSA might be main reason for OSA induced hypertension, and this might also be the vital cause of negative or modest effect of continuous positive airway pressure (CPAP) therapy on such hypertension. In clinical practice, more attention should be paid to the diagnosis and treatment of REM-OSA, which is of great significance for the prevention and treatment of OSA related hypertension.