BACKGROUND: In this study, we evaluated the predicted blood and effect-site C-50 for propofol and remifentanil target-controlled infusion and the Bispectral Index (BIS) values at loss of consciousness (LOC) and response to a standard noxious painful stimulus in Chinese patients. We hypothesized that these values would be different from previously published data on Caucasians. METHODS: Five medical centers enrolled 405 ASA physical Status I and II unpremedicated Chinese patients (97 men, 308 women) aged 18-65 yr. Propofol was initially given to a predicted blood concentration of 1.2 mu g/mL and thereafter increased by 0.3 mu g/mL every 30 s until Observer's Assessment of Alertness and Sedation score was 1. The propofol was kept constant, and remifentanil was given to provide a predict blood concentration of 2.0 ng/mL, and then increased by 0.3 ng/mL every 30 s until loss of response to a tetanic stimulus. BIS (version 3.22, BIS Quattro sensor) was also recorded. RESULTS: The propofol effect-site C-50 at LOC was 2.2 (2.2-2.3) mu g/mL. The remifentanil effect-site C-50 at loss of response to painful Stimulus was 3.3 ng/mL. Fifty percent of patients lost consciousness at a BIS value of 58, and 95%, had lost consciousness at BIS values <40. The BIS value at C-50 at loss of response to painful stimulus was 65.4, which was higher than that at LOS (P < 0.001). CONCLUSIONS: The predicted blood and effect-site concentrations of propofol and BIS values at LOC were lower than those in previously published studies of Caucasian Populations.