1. The effects of zopiclone 10mg (ZP), flunitrazepam 1mg (FN), triazolam 0.25mg (TZ) and levomepromazine 5mg (LP) on two models of sleep-wake schedule change-6 hours advanced shift: (A-shift), and 6 hours delayed: (D-shift)--were investigated in 6 healthy volunteers using polysomnography. 2. In A-shift with placebo, TST, SEI, %SR and REM/NREM decreased. ZP, FN and TZ shortened SL. All drugs increased TST and SEI. TZ and LP increased %SR and REM/NREM. 3. In D-shift with placebo, TST decreased, SWSL was prolonged, %S3+4 decreased, and %SR and REM/NREM increased. All drugs increased TST. ZP and LP shortened SWSL. All drugs increased %SWS. ZP, FN and TZ decreased %SR. ZP and FN decreased REM/NREM. 4. Daytime mental and physical conditions were worse than usual on more than half of the days in A- and D-shift. LP and FN caused some inadequate conditions on the following days. Significantly higher REM/NREM was observed in the nights before the days with worse mental conditions in D-shift, and lower REM/NREM in the nights before the days with worse physical conditions in A-shift. 5. It is concluded that TZ and ZP are superior to the others for A-shift and D-shift, respectively.