Rats of an initial body weight of 124 g were fed for 28 days on a casein diet unsupplemented or supplemented with grapefruit flavonoids (FL) 0.3% or inulin (IN) 5 and 10%, given singly or in combination. Feed intake and weight gain were registered and protein digestibility and N retention were determined. At the end of the experiment blood was sampled and concentrations of cholesterol (total and HDL), triacylglycerols (TAG), glucose, Mg, Ca and P were determined. FL fed either alone or with IN depressed feed intake, and FL+IN10 also body gain. The supplements did not affect feed conversion or protein digestibility, N utilization was or tended to be higher in rats fed IN singly or with FL. FL did not affect the total cholesterol level while IN fed alone tended to decrease, and fed with FL, significantly decreased total cholesterol. Both supplements tended to decrease TAG concentration.