A Post-sleep Inventory has been developed to permit an adequate description of subjective responses to a preceding sleep period. A factor analysis on a 2-wk. administration to 70 subjects is reported. Construct validity is assessed by demonstrating the scale's sensitivity in differentiating between subjectively designated “good” and “bad” nights of sleep and among three populations of individuals (“home sleepers,” college students, and an aged group). Construct validity is shown to be high.