Five fatty acids (FA) 2 saturated, palmitic (C16:0), stearic (C18:0) and 3 unsaturated, oleic (C18:1), linoleic (C18:2), arachidonic (C20:4) acids have been studied in the red cell membranes of breast cancer patients and controls. Statistically significant decrease in the risk of breast cancer has been found to be associated with increase in the levels of linoleic acid in pre-menopausal women and of arachidonic acid in the post-menopausal group.