14 prospective, randomized trials dealing with non-operated patients were analyzed. In all of them the presence of deep vein thrombosis was measured by the radioactive iodine fibrinogen uptake test. Various prophylactic regimens were tested. 13 studies concern patients after myocardial infarction and one a cerebral hemorrhage patient. Only 2 trials confirm the value of oral couramin administration for the reduction of deep vein thrombosis after myocardial infarction. Two studies show that prophylactic anticoagulation with a full dose of heparin reduces the incidence of deep vein thrombosis after myocardial infarction. In 3 studies, again after myocardial infarction, a statistically significant reduction in the incidence of deep vein thrombosis is found when small doses of heparin are given. In 1 study investigating a few patients no effect could be shown. Low doses of heparin reduce the incidence of deep vein thrombosis after acute cerebral hemorrhage. Early mobilization has reduced the incidence of deep vein thrombosis in 21 patients after myocardial infarction, as compared to 8 patients treated with bed rest. Heavy smokers suffering myocardial infarction show a statistically significant lower incidence of deep vein thrombosis than non-smokers, as 3 papers confirm.