The purpose of this study was to determine the effects of relaxation and imagery on the sleep of critically ill adults. The study was an experimental clinical trial with random assignment to two groups. Analysis used repeated measures ANOVA. Thirty-six adults (17 males and 19 females) with a variety of physical diagnoses in three critical-care units in two large metropolitan hospitals were studied. Outcome measures were scores on a visual analog sleep scale, measured on three mornings. The intervention was a combination of relaxation and imagery, delivered on two evenings. All subjects’ sleep improved over time. There were significant interaction effects between the intervention, gender, and time, with males’ scores improving rapidly, and females’ scores first dropping, then improving rapidly. A combination of relaxation and imagery is effective in improving the sleep of the critically ill adult, with men responding immediately to relaxation and imagery with improved sleep, and women taking more time to respond to the intervention.