Résumé : Preincubation of human neutrophils with chemotactic concentrations of 5(S)-hydroxy-eicosatetraenoic acid (5-HETE) or 5(S), 12(R)-dihydroxy-6,14 cis-8,10 trans-eicosatetraenoic acid (leukotriene B4) induces a state of preferential chemotactic unresponsiveness to the homologous factor, termed deactivation, and less suppression of the responses to other chemotactic stimuli. The ratio of the concentrations required for maximal chemotactic deactivation of neutrophils to that which stimulates chemotaxis optimally is greater for 5-HETE and leukotriene B4 than for peptide and protein factors. In contrast to other chemotactic factors, 5-hydroperoxy-eicosatetraenoic acid (5-OOHETE) induces neutrophil chemotactic deactivation that is independent of the nature of the subsequent stimulus and is more slowly reversible after elimination of the fluid-phase deactivating factor. The unique characteristics of the chemotactic deactivation of human neutrophils by 5-OOHETE may be attributable in part to its endogenous metabolism to potent deactivating factors or to covalent derivatization of subcellular structures of the neutrophils by the highly reactive 5-OOHETE.