The time of onset and duration of tlie anti recall action of Iorazcpam were assessed under clinical conditions by measuring recall and rccognition of visual stimuli 24 hours after intravenous administration of Iorazepam. The visual stimuli were first presented 5–240 minutes after 2 mg and 5–360 minutes after 4 mg Iorazepam. Retrograde amnesia was not produced. Lorazepam, 2 mg produced a short anti-recall effect (enterograde amnesia) in 50 per cent of the cases with a latency of 30 minutes and a duration of less than half an hour. Duration and frequency of the anti-recall effect were greater after 4 mg while the latency was shorter. More than 70 per cent of the individuals tested were amnesia for the visual stimuli 15 minutes to 4 hours after 4 mg lorazepam. Sedation was satisfactory and long-lasting following both doses of lorazepam, but was not related to the antirecall effect.