AbstrctThis study was descriptive research aimed to determine the characteristics of sleep pattern in Thai children (0-3 years old). Comparison of sleep efficiency in terms of sleep efficiency index (SEI), the time spent in each sleep stage (stage 1, 2, 3, 4 and rapid eye movement (REM) sleep), sleep latency (SL), and total sleep time (TST) between the night and day time were presented. In the comparison of the sleep efficiency between night and day time recordings of the participants, the mean percentage of the stage 1 NREM sleep during the night time was longer than during the day time with statistically significant difference between the two recording periods at level of.05. Stage 2 non-rapid eye movement (NREM) sleep during the night time was also longer than during the day time, but no statistically significant difference. The mean percentage of stage 3, 4 NREM and REM sleep during the night time were shorter than during the day time. There was no statistically significant difference between the two periods. The mean duration of SL during the night time (19.88±1.44 minutes) was longer than during the day time (21.29±2.06 minutes), but no statistically significant difference. The mean duration of TST during the night time (7.05±0.25) was longer than during the day time (0.91±0.10). In the same way, the mean duration of SL during the night time (9.72±0.18) was longer than during the day time (4.82±0.13). Also, the average SL during both periods of recording was longer than TST.