tion, the ratio of arachidonic acid to eicosapentaenoic acid in the patients' neutrophil cellular lipids decreased from 81:l to 2.7:1, and the mean generation of leukotriene B4 (with calcium ionophore stimulation) significantly declined by 33%. The mean neutrophil chemotaxis to both leukotriene B4 and FMLP significantly increased toward the normal range at week 6. The generation of 5-lipoxygenase products by calcium ionophorstimulated monocytes was not significantly suppressed, but a significant decline (37 %) in plateletactivating factor generation was noted at week 6. The modulation of these measures of leukocyte inflammatory potential suggests that fish oil supplementation may have an antiinflammatory effect.Dietary supplementation with fish oil fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) in healthy volunteers has been shown to increase the relative content of EPA in leukocyte membranes and to decrease the response of the leukocytes to both transmembrane and calcium ionophore activation (1). The chemotactic dosedependent response of neutrophils to leukotriene B4 (LTB4) was significantly suppressed at 6 weeks of supplementation, and the chemotactic sensitivity was restored when the supplement was discontinued. The 5-lipoxygenation of arachidonic acid in response to activation with calcium ionophore was inhibited at 2 points. Fatty acid hydrolase function was attenuated, as defined by a reduced release of labeled arachidonic acid from prelabeled neutrophils and monocytes. Function of the 5-lipoxygenase enzyme (Figure 1) was suppressed, as determined by reduced generation of the sequential arachidonic acid-derived reaction products, 5-hydroperoxyeicosatetraenoic acid (measured