Background: Propofol is the most commonly used anesthetic for sedation and target-controlled infusion (TCI) is useful for dental treatment. However, it is important to assess and maintain an adequate depth of sedation in patients with severe intellectual disabilities Therefore, in this study we aimed to evaluate the adequate propofol target concentration for dental treatment in severely intellectually disabled patients. Methods: We undertook retrospective review of the sedation records of severely intellectually disabled patients who underwent dental treatment under TCI propofol sedation from September 2011 to April 2012. We evaluated the initial target concentration, stabilized concentration of propofol and monitored vital signs, including BIS score using sedation records. Results: Total 20 patients (10 male and 10 female patients) were included in the study. Every participant was severely intellectually disabled. The mean sedation duration was $70{pm}16$ (45-100) minutes. The initial propofol target concentration infusion amount was $2.7{pm}0.45$ (2.0-3.0) mcg/ml. The propofol effect site concentration (Ce) was $2.6{pm}0.7$ (1.0-4.0) mcg/ml. The average value of BIS was $52.6{pm}13$ (28-81). During the treatment period, there were no severe complications. Conclusions: The average propofol Ce for deep sedation without any complications in intellectually disabled patients was 2.6 mcg/ml.