The effect of Lipo PGE1 (prostaglandin E1 incorporated in lipid microspheres) on laurate-induced peripheral arterial occlusive disease in rats was evaluated and compared with that of other related compounds. Lipo PGE1 showed a potent inhibitory effect on the progression of lesions in this model, but Lipo PGA1 had no such effect. Moreover, the effect of Lipo PGE1 was more potent than that of PGE1 X CD (cyclodextrin clathrated PGE1) and PGE1 on this model. These results suggest that incorporation of PGE1 into soybean oil microspheres might exert a more potent effect by facilitating drug delivery to the lesions in this model. It would appear that Lipo PGE1 is suitable for clinical use in peripheral vascular disorders.