This double-blind parallel groups study investigated the effects of 7.5 mg midazolam on transient insomnia caused by eastward and westward multiple time zone flights. Three groups of six subjects each were treated with either midazolam or placebo during the first four post-flight nights in both directions. Sleep-wake behavior was monitored throughout the study by actigraphic recordings from the wrist of the non-dominant hand in 1 min bins and by morning questionnaires. The results showed that midazolam significantly lengthened sleep and increased the percentages of bins defined as sleep after the eastward flight. These results are discussed in view of recent findings that short-acting benzodiazepines induced phase shifts in mammalian circadian rhythms.