22 patients, randomly selected over the age of 40 years, undergoing an ophthalmic operation, lasting more than 30 min under general anaesthesia, were investigated for the development of postoperative deep vein thrombosis. The diagnosis was made by clinical examination, [<sup>l25</sup>I]-labelled fibrinogen method and Doppler ultrasound technique. Only one patient developed a postoperative deep vein thrombosis (4.5%) which was asymptomatic and extended from the calf to the popliteal vein without pulmonary embolization. This is in contrast to the incidence in general surgical patients which varies between 28 and 51 %. The possible reasons are related to the minimal tissue trauma and early mobilization of the ophthalmic patients.