In a prospective study 99 consecutive patients admitted for elective aorto‐coronary by‐pass surgery were subjected to estimation of their fibrinolytic capacity.Reevaluation after 16 months included shunt angiography and repeated testing of the fibrinolytic capacity.In the total material consisting of 244 grafts (2.7 per patient) 76 (31%) were occluded. In the subgroup of 24 patients with reduced fibrinolytic capacity, 25 (38%) of the 66 grafts were occluded as compared to 53 (30%) of the 178 grafts in patients with normal fibrinolytic capacity (p = 0.2). The number of grafts per patient and the values of the peroperatively measured blood flow in the grafts were similar in the 2 groups.Looking into the subgroup of grafts with “poor flow values” as measured peroperatively (≤ 35 ml/min), 14 (78%) of 18 grafts were occluded in patients with reduced fibrinolytic capacity, whereas 28 (53%) of 53 grafts were occluded in patients with normal fibrinolytic capacity (p = 0.06).In conclusion, the present study is thought to indicate that reduced fibrinolytic capacity might be an additional risk factor for graft occlusion in patients undergoing aorto‐coronary by‐pass surgery, particularly so in grafts where low blood flow values