The pattern of recovery sleep after sleep deprivation was investigated in healthy young adults. Six subjects experienced three experimental conditions (0, 24, and 48 hr sleep deprivation) in a Latin Square design. The recovery period consisted of a 24-hr enforced time in bed during which subjects were polysomnographically recorded beginning at 0800. To assess the differential effects of the deprivation conditions, the total sleep time on the 24-hr recordings was submitted to a six (4-hr block) by three (deprivation condition) multivariate analysis of variance. Subjects slept more following the 24- and 48-hr conditions when compared to the 0-hr condition. Across conditions, subjects slept more during the first 4 hr when compared to the remaining five blocks. Importantly, there was a significant interaction of sleep deprivation by 4-hr block. In block 1 sleep was differentially recovered between each condition with more sleep being recorded following longer hours of deprivation. In block 2 subjects in the 24- and 48-hr conditions slept comparable amounts and significantly more than those in the 0-hr condition. In blocks 3 and 4 only the 48-hr condition exhibited significantly more sleep than the 0-hr condition. However, significantly less sleep was found in block 6 following the 48-hr condition. Overall, subjects recovered 72% and 42% of the total amount of sleep lost during the 24- and 48-hr conditions, respectively.