Eighteen healthy children, 9 boys and 9 girls, between 8 and 12 years of age were examined with polygraphic sleep records, multiple sleep latency tests (MSLTs), and measurements of reaction times. Sleep was recorded at home on Oxford Medilog 9 channel cassette tape recorders (Oxford Medical Systems, Abingdon, U.K.) and sleep staging was performed from the screen of the display unit. Two consecutive nights were recorded. MSLT was done in the laboratory. The subjects were given 30 min to fall asleep on four occasions during the day after the last recorded night of sleep. Reaction times were measured repeatedly between each MSLT trial. More slow wave sleep was found in this study compared to others. Also, the first night effect was slight. It is proposed that this is due to the fact that the recordings were performed at home. The initial sleep cycle was incomplete in almost all subjects. A sleep stage with traits of both rapid eye movement (REM) and non-REM could be seen in this cycle, probably representing an abortive REM period. MSLT confirmed the low daytime sleepiness in healthy preadolescent children. A sleep latency of 10 min or less on two or more sleep trials, or a daily mean sleep latency of less than 20 min, is rarely seen in this age group. The reaction times were within normal limits for the age of the subjects. Nighttime sleep values, daytime sleep latencies, and reaction times were not correlated in these normal-sleeping children.