Prostaglandin E1 (PGE1) suppresses leucocyte effector function and reduces inflammation in several animal models of acute and chronic inflammation. A drawback to its use as a therapeutic agent is the relatively high doses needed to suppress inflammation. We present evidence in this report that liposome associated PGE1 (LAP) reduces markedly acute inflammation induced in a subcutaneous air pouch by monosodium urate crystals, and by the polypeptide mediators, interleukin 1-beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). A single dose of 12 micrograms/kg LAP given intravenously 2 hr after inflammation was induced, reduced accumulation of cells and exudate by 31-49%.