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.