The effect of oral ingestion of different fractions of onion (Allium cepa)-extract, residue, and whole-at a dose level equivalent to intake of 50g of onion per day for a 70-kg man, for 30 days, to male adult, normal, albino rats was studied on blood and erythrocyte membrane lipids and certain membrane-bound enzymes. Onion extract and residue showed hypercholesterolemic effect, while whole onion showed hypocholesterolemic effect in blood. In erythrocyte membranes, all the fractions had hypocholesterolemic and hypolipidemic effect, which was accompanied by changes in the erythrocyte membrane enzymes studied, i.e., alkaline and acid phosphatase, 5'-nucleotidase, total and Mg2+ ATPase. The above study indicated that it is safer to take whole onion rather than onion residue or extract, because whole onion could lower the blood cholesterol level even in normal condition and has a less pronounced effect on the micro-evironment of the cells.