OBJECTIVE We used quantitative analysis of the electroencephalogram (EEG) during routine clinical practice to assess the effect of tracheal intubation following induction of anesthesia with propofol and fentanyl. METHODS The topographic EEG was recorded from eight bipolar electrode derivations in 25 patients. Z-scores relative to age expected normative data were computed for relative power in the delta, theta, alpha and beta frequency bands. Multivariate statistics (Hotellings' t-sqare) were used to evaluate changes in regional brain electrical activity. RESULTS Tracheal intubation induced an increase in alpha and beta frequencies, while delta power was reduced (F-values: Delta: 7.68, p = 0.011; Alpha 31.93; p < 0.001; Beta 12.85, p = 0.001). The most pronounced regional effect was seen for the alpha frequency band with the largest increase in both fronto-temporal regions (F-value 33.89, p < 0.001). During clinical practice the patients received propofol 2.7 (+/- 1.2; minimum: 0.5, maximum 6.9) mg kg (- 1) and fentanyl 2 (+/- 1; minimum 1, maximum 4) microg kg (- 1). Vital parameters did not change during intubation. CONCLUSIONS Individual titration of the dose of propofol and fentanyl as done during routine clinical practice is not sufficient to block the strong noxious stimulation of intubation. Tracheal intubation resulted in "classical" cortical arousal. It remains open whether this cortical wake-up phenomenon has a clinical impact.