To investigate the differences between good sleep and poor sleep, 41 sleep records were observed with nine normal male subjects ranging in ages from 22 to 40 years. A comparison was done of the differences of sleep records between the good and poor sleep estimations for each subject. 2. Poor sleep showed significantly shorter total sleep time (P less than 0.01) and significantly shorter stage 2 (P less than 0.05) than good sleep, but there were no differences in stages 1, 3, 4, stage REM, the percentage of every sleep stage to total sleep time, REM latency, mean REM duration, REM cycle and REM density. 3. Poor sleep showed longer latency for falling sleep (P less than 0.10) and a significant increase in stage changes from stage 2 to stage 3 (P less than 0.01) than with good sleep. 4. Poor sleep showed more prolonged awakenings and significantly longer durations spent for awakenings (P less than 0.05). 5. As to awakening in the morning poor sleep showed longer times required from terminal stage 2 and stage 4 and a significantly shorter time from terminal stage REM (stages 2 and 4, P less than 0.10, REM, P less than 0.01). 6. A certain amount of stage 4 and its decreasing seemed to be delayed in poor sleep, though its initial appearance wasn't. 7. REM periods of good sleep peaked at the third or the fourth REM stage and decreased to the fifth but those of poor sleep showed a gradual increasing from the second to the fifth having almost the same durations. 8. Awakenings in the morning often occurred from stage REM or just after an REM stage in poor sleep but in good sleep, on the other hand, occurred from stage 2. 9. The thresholds of natural wakenings from stages 3, 4 and REM of good sleep during the night might be higher than those of poor sleep.
