A review of the literature is undertaken to account for the current status of acetylsalicylic acid (ASA) in the treatment of patients with arterial thrombo-embolic conditions. Employment of ASA monotherapy has been documented to be effective in clinically controlled investigations in patients with unstable angina pectoris, transient cerebral ischaemia, coronary by-pass and femoro-popliteal endarterectomy and introduction of vascular prostheses and, in addition, in primary and secondary prophylaxis of acute myocardial infarction (AMI). In combination with dipyridamol, ASA has been found to be effective in secondary AMI prophylaxis, coronary by-pass operation and in peripheral arteriosclerosis. In patients with cardiac valvular prostheses, conventional anticoagulation therapy must still constitute the basic treatment but dipyridamol may be employed to increase the antithrombotic efficacy of the treatment. The dosage of ASA in the majority of works has been about 1,000 mg daily while isolated investigations have shown good effect from doses as low as 60 mg daily. It appears to be important for the efficacy of the treatment with platelet inhibitors in the above-mentioned conditions that treatment is instituted rapidly and, in connection with operative intervention, preferably preoperatively. In other clinical conditions such as preeclampsia, hypertension in pregnancy, diabetic angiopathy and nephropathy, membranoproliferative glomerulonephritis and arterio-venous shunts with haemodialysis, treatment with ASA appears to be effective but documentation in extensive clinically-controlled investigations is not yet available. The duration of treatment with ASA in arterial thrombo-embolic disease does not appear to be illustrated unanimously in the articles published but, as the atherosclerotic lesion is not influenced by ASA, there are indications for life-long therapy.