The authors prospectively assessed intraindividual variability in propofol dosage for induction of sedation in repetitive procedures in children with malignancies. A total of 80 procedures were performed in 24 children. Primary outcome measure was the intraindividual propofol dose required to achieve adequate sedation. Intraindividual variability in propofol dosage required to achieve adequate sedation was 0.0-2.2 mg.kg-1. Twenty-five percent of the patients had a dose range of 0.0-0.5 mg x kg-1; 37.5%, >0.5-1.0 mg x kg-1; and 37.5% >1.0-2.2 mg x kg-1. Due to remarkable intraindividual differences, propofol dosage should be titrated toward the desired level of sedation.