Butter oil is the major cooking oil of the nomadic Fulani of the western Sahel of Africa. It is made from cow's milk and is consumed by all members of society, including pregnant women. In an e!ort to learn the reasons why the milk of Fulani women contains relatively low percentages of several nutritionally important fatty acids, linoleic acid and docosahexaenoic acid (DHA) in particular, we obtained butter oil in a local market in Kurra Falls, Nigeria and analyzed it for its fatty acid composition. Fatty acid analysis by gas}liquid chromatography revealed that while the butter oil purchased in a local market in Kurra Falls in northern Nigeria contained nutritionally adequate proportions of -linolenic acid (1.09%), it was a poor source of linoleic acid (1.74%), DHA (0.03%) and arachidonic acid (0.14%). Since butter oil is the cooking oil that is most widely used by the Fulani, the low proportions of critical polyunsaturated fatty acids it contains helps explain the low levels of linoleic acid and DHA in the milk fat of lactating Fulani women. In addition, the low content of polyunsaturated fatty acids in butter oil may ultimately have implications for the general nutrition and growth and development of infants who are exclusively breast-fed by Fulani mothers whose major dietary fat source is butter oil.