Fatty acid composition of phosphatidylinositols was analyzed in peripheral blood lymphocytes from nine alcoholic patients who were well nourished and without severe acute and chronic liver disease, before and after stimulation with anti-CD3 antibody. Six comparable nondrinkers were studied as controls. A reduction in unsaturated fatty acid (mainly arachidonic) and an increase in palmitic and stearic acid molar content were observed in phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), and phosphatidylinositol-4,5-bisphosphate (PIP2) in unstimulated samples from alcoholic patients in comparison with normal subjects, leading to a significant decrease in the saturated/unsaturated ratio. In controls, anti-CD3 stimulation caused a marked decrease in arachidonic acid relative molar content counterbalanced by an increase in other polyunsaturated fatty acid relative molar content in PI, PIP, and PIP2 fractions. Interestingly, after anti-CD3 stimulation, alcoholic patients show the same trend of modification in the fatty acid composition resulting in a sharp reduction of arachidonic acid relative molar content. These results support the hypothesis of an alteration in nutrients being responsible for immune derangement in alcoholics.