Flunitrazepam (0.015 mg/kg) was injected i.v. into 20 patients, ages 19-79 years, as a sedative agent prior to epidural anesthesia. The concentrations of unchanged flunitrazepam in sea were determined by 63Ni-EC-GLC, and the pharmacokinetic parameters were calculated using the two-compartment open model. Age as such had no effect on the kinetics of flunitrazepam, but its sedative effect was clearly increased in the group over 60. No correlation between the serum level or elimination half-life and sedation was found. Generally, flunitrazepam's strong and rapid sedative effect renders it a useful adjuvant in connection with epidural anesthesia.