Examined the effects of brief and long daytime naps following nocturnal sleep restriction. During a 3-wk period, 12 individuals participated in a repeated measures design comparing the effects of no naps, 10-min, and 30-min afternoon naps following 4.7 hrs night sleep. Collected data included EEG and electrooculogram (EOG) recordings, and objective–subjective alertness and cognitive performance measures were taken before naps and 5, 35, and 60 min following. Results show that alertness and performance were unchanged for the no nap condition. Following 10-min naps, there was immediate and sustained improvement in subjective alertness and cognitive performance. Immediately following 30-min naps, alertness and performance measures declined but recovered 1-hr postnap. Findings suggest that the delayed benefits following 30-min naps are due to sleep inertia. It is concluded that 10-min afternoon naps rapidly and significantly ameliorate the detrimental effects of sleep restriction. (PsycINFO Database Record (c) 2012 APA, all rights reserved)