Circadian disturbances in relation to surgery have been extensively researched through the latest couple of decades. Surgery has been shown to affect melatonin rhythm, core body temperature, cortisol rhythm, activity rhythm and sleep in the perioperative period. The changes translate into both subjective patients' discomfort, prolonging convalescence and clinical effects on morbidity and mortality. Future research should be performed to show effect across different surgical procedures and to investigate potential interventions to alleviate harmful effects of circadian disturbances.