A middle-aged female patient with chronic insomnia showed rapid eye movement (REM)- localized obstructive sleep apnea. She visited the Sleep Disorders Clinic and complained of insomnia with loud snoring. Once, in the past, her sleep complaints had disappeared after weight reduction but, 6 months later, she complained of excessive daytime sleepiness. Overnight polysomnography revealed REM-localized apnea. Careful follow up is strongly recommended for a female patient with chronic insomnia who shows REM-localized apnea.