Five hundred patients were questioned and assessed on the day before operation and the presence of pre-operative anxiety noted. In each case an attempt was made to correlate the incidence of anxiety with the patient's sex, age, weight, physical and social status, operation proposed, previous hospital experience and sedative therapy. A significantly higher incidence of anxiety was found (1) in females than males, (2) in females up to and including 11 stones weight (70 kg) than in females over this weight, (3) in patients previously or currently on sedative therapy. The causes of pre-operative anxiety as stated by the patient are listed and discussed.