<qa>  What is the impact of advance age and presence or absence of sufentanil during propBispectral index BIS is widely used to estimate the depth of anesthesia. In clinical studies, a large variability of BIS has been observed. Several factors may be responsible for this inconsistency. We were able to show that in elderly patients average age 78 years receiving increasing doses of propofol alone a BIS values at loss of consciousness LOC were about 30 higher compared with young patients average age 35 years. We showed also that in young patients average age 48 years the BIS values at LOC were significantly higher in those receiving sufentanil concomitantly with propofol compared with those who had received propofol alone. It remains unknown, however, whether these data from young surgical patients are applicable to a population of elderly patients. It may be argued that in the elderly receiving propofol, the impact of advance age was so important that any addition of an opioid would not further disturb the sedation-monitor balance. Alternatively, it may be expected that in the elderly receiving an opioid added to propofol the impact of both drugs on sedation will be additive and that previous observations from younger patients will be further exaggerated. The impact of advance age and presence or absence of sufentanil during propofol induction on BIS values at LOC was investigated in this trial. 