Melatonin is a hormone mainly produced in the pineal gland. The most well known effect is a modulation of the circadian rhythm. Patients undergoing surgery often get a disruption of this rhythm. Effects of melatonin have been examined in several randomised clinical studies. In this report we briefly review evidence regarding anxiolytical, analgesic and sedative effects of melatonin in relation to surgery. Studies show an effect in favour of medication with melatonin with regards to sedation and anxiety but the effect on analgesia has yet to be clarified with further clinical studies.