We considered the use of hemoperfusion in the treatment of severe intoxications frequently seen in the Netherlands, primarily involving barbiturates and especially Vesparax (a combination of secobarbital, brallobarbital and hydroxyzine HCl) overdoses. In about 60% of the cases in which hemoperfusion seemed indicated, at least one barbiturate was involved; in about 20%, a Vesparax poisoning was found. From the obtained results it has been proven that for an adapted evaluation of hemoperfusion, in most cases it is not sufficient to determine merely the pre- and post-perfusion plasma levels, but also plasma levels have to be monitored during perfusion at the in- and out-let of the hemoperfusion column. Using these data, clearances and the total amount of drug removed were calculated. A comparison has been made with the elimination by forced diuresis. In some cases plasma elimination half-life values during and after perfusion have been computed and compared.