Blood coagulability was studied in patients with ischaemic heart disease and microthromboses in the microcirculation as seen when examining the vessels of the bulbar conjunctiva. Appearance of single microthrombi in the microcirculatory bed was not accompanied by change of blood coagulability as compared to such patients without microthrombi. With multiple microthrombi increase of haemocoagulation properties and of thrombocyte aggregation was noted, more marked with multiple microthrombi in the venules and capillaries. With further spread of the process to arterioles the hypercoagulation tendencies were retained with signs of utilization of coagulation factors, which can be interpreted as disseminated intravascular coagulation.