For both of the PSGs, you will arrive at the M. D. Anderson Sleep Center at about 7:30 p.m. You will complete a questionnaire about your sleep the night before and your activities during that day. You will also complete a questionnaire that asks about any 'dozing off' habits you may have. It should take about 10-15 minutes to complete the 2 questionnaires. You will be taken to a sleep room, which will be quiet and darkened. A registered PSG technologist will place the sensors on your body. You will be allowed to sleep until your usual wake-up time, as noted on your sleep diary. Soon after you wake up, the sensors will be removed. You will complete a third questionnaire about your night's sleep. This last questionnaire should take about 5-10 minutes to complete. You will be able to leave shortly after completing the questionnaire.