 Remifentanil has been shown to reduce propofol requirements during induction and maintenance of anaesthesia. 56 Also modest doses of remifentanil markedly reduce the amount of propofol required to ablate response to painful stimuli. The relationship between propofol and remifentanil has been reported as synergistic but additive when using propofol concentrations within the clinical range. 78 However in other studies, BIS has shown no interaction between propofol and remifentanil 910 A correlation between BIS, painful stimuli and other opioids has been demonstrated. 11 It has been suggested that BIS values can change with propofol and painful stimuli and this can aid administration of remifentanil in a dose dependent manner. 12 Since propofol and remifentanil are ubiquitously used together, the interaction between these drugs and EEG needs to be defined in more detail. 