AbstractThe effects of zopiclone 7.5 and 15 mg, triazolam 0.25 and 0.5 mg, flunitrazepam 1 and 2 mg, ethanol and placebo on performance, mood and sleep onset latency after partial sleep deprivation, were compared in a randomized, double‐blind, crossover, single‐dose study. Sixteen healthy volunteers of both sexes, aged 21–31 years, were included in the study. The overall assessment of the total psychological measurement indicated that zopiclone 7.5 mg, triazolam 0.25 mg and ethanol (Cmax= 0.40 parts per thousand) did not affect the daytime performance of an unacceptable degree even when given late at light. The findings for flunitrazepam 1 mg were not so uniform, but also seemed acceptable. Zopiclone 15 mg, triazolam 0.5 mg and flunitrazepam 2 mg were rated as not acceptable alternatives. No significant differences were shown concerning mood. The overall assessment for sleep onset latency and subjective alertness indicated that zopiclone 7.5 mg and triazolam 0.25 mg had a more appropriate profile than the other drugs and doses t