Objective To study the effect of gender and ages on predict blood and effect-site EC50 for propofol and remifentanil TCI and bispectral index at loss of consciousness and response to a standard noxious painful stimulus. Methods 405 ASA Ⅰ-Ⅱunpremedicated Chinese patients in 5 medical centers for elective operation were involved. Patients were allocated to 4 groups according to ages (group1: 18