Fructooligosaccharide-supplemented whey drinks may have potential as an interventional strategy for lowering cholesterol and triglyceride levels in dyslipidaemic conditions. A bioefficacy study was conducted in normal, hypercholesterolaemic and hyperglycaemic Sprague Dawley rats, running two consecutive trials for validity of results. Control drink (T-0), whey drink (T-1) and whey drink supplemented with 1.5% fructooligosaccharides (T-4), were given to each group. The functional drink caused a significant reduction in serum total cholesterol, low density lipoprotein (LDL) and triglycerides, and an increase in high density lipoprotein. The greatest decline in total cholesterol was induced by T-4 (10.9% and 12.0% in hypercholesterolaemic rats and 7.0% and 7.7% in hyperglycaemic rats, for trials 1 and 2, respectively). The decrease in total cholesterol by T-4 was mainly due to a pronounced decrease in LDL cholesterol (14.7% and 16.1% in hypercholesterolaemic rats and 7.4% and 8.1% in hyperglycaemic rats for trials 1 and 2, respectively).