Lipid extraction of adult O. volvulus worms using a chloroform/methanol/water mixture yielded 10 lipid fractions of which 8 were demonstrated by the orcinol reagent to be glycolipids. In TLC, two of these lipid fractions had mobilities similar to cholesterol and cholesterol ester (Rf.: 0.95, 0.86) whereas two others migrated as sphingomyelin and lecithin (Rf.: 0.40, 0.35) respectively. Other components migrated at intermediate positions. The glycolipids were immunologically active and reacted with sera from onchocerciasis patients. The highest reaction was obtained with the IgG antibody class, followed by IgM while no appreciable reactivity was observed with IgE. Sera from patients infected with other filariae such as Loa-loa and Dipetalonema perstans did not show any significant reaction with these antigens. The significance of these results is discussed.