We studied 30 female patients undergoing elective surgery, to assess the reliability of electroencephalogram spectral edge frequency and median frequency to predict loss of consciousness and movement in response to skin incision during total intravenous anaesthesia. Each patient received a different combination of propofol (1, 2, 3, 4, 5, or 6 μg.ml−1) and sufentanil (0.1, 0.2, 0.3, 0.5 or 1.0 ng.ml−1) target concentrations for induction of anaesthesia using target controlled infusions, assigned randomly. In a logistic regression model, spectral edge frequency was a significant determinant of both loss of consciousness (p = 0.0006) and movement to skin incision (p = 0.0044), whereas for median frequency no significant prediction model could be established. The probabilities of 50% and 95% no response for spectral edge frequency were 13.4 Hz and 6.8 Hz, respectively. The variability of the data limited the predictive value, so that spectral edge frequency was a poor predictor and median frequency was no predictor of response in the individual patient during total intravenous propofol/sufentanil anaesthesia.