['Septic shock and its effects are a major cause of mortality in the intensive care environment. The exact effect and mechanism of endotoxin has yet to be fully described. With a better understanding of this process, better clinical tools could be developed to treat these patients.', 'Endotoxin has no direct effect on human skeletal muscle microvasculature and requires the release of an endothelial-derived factor to produce the vasodilation seen in gram-negative sepsis.', 'Benchtop research using an isolated arteriole model with controlled exposure to endotoxin.', 'University medical center.', 'First-order arterioles (approximately 150- micro m diameter) were isolated from human cremasteric muscles and pressurized to physiologic levels before exposure to an endotoxin-rich effluent with and without an upstream conduit vessel (superficial epigastric vein). The vasodilatory effect was measured with videomicroscopy and compared with control samples.', 'Mean vessel diameter and percentage of loss in tone.', 'When compared with controls, the isolated arteriole had no significant response when exposed to endotoxin alone (3.5% change in basal tone). When the endotoxin was allowed to pass over an upstream conduit vessel, the arteriole showed marked dilation (14.2% loss of basal tone).'] Does endotoxin have an indirect vasodilatory effect on isolated human skeletal muscle arterioles?