Sleep-wake habits in middle and late adolescence were surveyed for college of technology (n=799), college of nursing (n=460) and university (n=1062) students. Daytime sleepiness and nodding off were often occurred. They made up for shortened sleep time at holiday. One third of them took replacement naps. Some of them had the irregular life habits, such as delayed bed-time, shortened sleep time, irregular meal time and engaging in night work, suggesting that these habits might alter the phase of circadian activity cycle. Finally, the criteria for the choice of subjects on sleep research were discussed.