The invention relates to monitoring of pain-related responses in a patient in order to detect the level of pain experienced by the patient. At least one first measurement signal is acquired from the patient and at least one of the signals is transformed into a normalized signal having a predetermined value range. Based on the at least one normalized signal obtained in this way, a threshold condition is set and a rate at which at least one second measurement signal fulfills the threshold condition is monitored, wherein each of the at least one second measurement signal is derivable from a corresponding normalized signal and indicative of pain-related activity in the patient. The level of pain experienced by the patient depends on the rate monitored.