The aim of this retrospective study of 50 deep vein thromboses (DVT) of the lower limbs in patients aged 80 and over (35 women, including 2 with bilateral DVT and 13 men), mean age 83.37 +/- 2.72, hospitalised in a department of cardiology, was to assess the diagnostic value of ultrasound investigations, clinical parameters and results of treatment of thrombo-embolic disease in this age group. High DVT were found in 76 per cent of cases and pulmonary embolism occurred in 52.1 per cent of cases, its incidence increasing with age. One third of DVT were asymptomatic and presented as pulmonary embolism, the predominant clinical feature being edema in the absence of other signs. The existence of atrial fibrillation was associated in 90 per cent of cases with a pulmonary embolism. Venous Echo-Doppler is also the key investigation in the diagnosis of thrombo-embolic disease. Cardiac Echo-Doppler seems particularly useful in the diagnosis of pulmonary embolism when more than 40 per cent of the vascular bed is cut off. Thrombolytic treatment remains possible after the age of 80 in life-threatening situations. Overall hospital mortality remains high (10.4 per cent) and appears to be due chiefly to the onset of a pulmonary embolism which is not thrombolyzed since considered insufficiently serious or occurring in a situation in which fibrinolysis is theoretically contra-indicated.