Although prostaglandin El (PGE ) has been clinically available for a long 1 time, only in recent years has its effectiveness in peripheral arterial occlusive disease been confirmed in controlled studies. Not surprisingly, the favour- able results achieved both in patients with critical limb ischaemia and in those with intermittent claudication has stimulated research activities into the clinical pharmacology of this prostaglandin. As a consequence of these efforts, exciting new findings have revealed that PGE has anti thrombotic , endothelium-stabilizing and leucocyte-stabi- 1 lizing properties as well as effects on lipid metabolism, all of which, quite apart from its well-known anti-aggregating and vasodilator effects, may add to the clinical efficacy of the substance. New data have also been gathered on the metabolism of PGE most b notably the detection of 13, 14-dihydro-PGE a metabolite which was b recently isolated in humans following the administration of PGE . Being 1 biologically active, the pharmacodynamic spectrum of 13, 14-dihydro-PGE 1 very closely resembles that of PGE . This finding may help to explain the 1 efficacy of PGE despite its rapid metabolization when given intravenously.