An open-label, dose-escalation study was conducted to determine doses of lorazepam required to induce anterograde amnesia and sedation in children without producing excessive toxicity. Oncology patients 4 to 17 years of age undergoing lumbar puncture or bone marrow aspiration were eligible; a patient could be entered in the study for a second procedure at a different lorazepam dose. A single oral dose of lorazepam was administered 45-60 minutes before the procedure. Starting with 0.02 mg/kg, the same dose was given to three patients; if no dose-limiting effects occurred, dose was increased by 0.01 mg/kg. Before the procedure the patient was shown a toy that he or she was later asked to identify. Immediately after the procedure (usually 60-75 minutes after the lorazepam dose), sedation was assessed on a scale of 0 (alert) to 4 (coma), and the clinician performing the procedure was asked to subjectively evaluate sedation. Patients were rated for amnesia 24 hours after the procedure; a scale of 0 (recalls procedure and toy without prompting) to 4 (recalls nothing since procedure) was used. Twenty patients received 28 doses of lorazepam. The study was terminated when two patients who received 0.10 mg/kg had excessive ataxia. Sedation was subjectively considered adequate for 24 of the procedures. Sedation and amnesia scores were not well correlated with increased dose. Amnesia occurred in some patients with doses as low as 0.03 mg/kg. In children undergoing lumbar puncture or bone marrow aspiration, premedication with oral lorazepam 0.02-0.09 mg/kg generally produced adequate sedation for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)