Previous reports of our laboratory have shown that PUFA (n-6)-rich diets cause important changes of the metabolism of the immune tissues. In this study, alterations of macrophage metabolism and function were examined in rats fed polyunsaturated (UC) or saturated (SC) fatty acids-rich diets during 6 weeks. The UC group decreased intraperitoneal cell migration and macrophage phagocytosis. These changes were related to modifications of macrophage metabolism. The UC group showed also increased G-6-PDh in inflammatory macrophages. These findings suggest that pentose-phosphate pathway is not the unique metabolic factor to control phagocytosis. PUFA-rich diet reduced glutaminase activity. Therefore, this amino acid might be one of the possible metabolic reasons for the impaired macrophage function observed.